feat: added region color customization feature

src/components/common/ColorPalettePopup.css

@@ -0,0 +1,62 @@
+.color-palette-popup {
+  background: #2d2d2d;
+  border: 1px solid #444;
+  border-radius: 6px;
+  box-shadow: 0 6px 18px rgba(0, 0, 0, 0.35);
+  padding: 8px;
+  width: max-content;
+}
+
+.color-palette-popup button {
+  appearance: none;
+  -webkit-appearance: none;
+  border: none;
+  outline: none;
+  box-shadow: none;
+}
+
+.color-palette-none {
+  width: 24px;
+  height: 24px;
+  margin: 0 0 2px;
+  padding: 0;
+  border-radius: 5px;
+  background: #383838;
+  color: #e0e0e0;
+  cursor: pointer;
+  font-size: 12px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.color-palette-none:hover {
+  background: #444;
+}
+
+.color-palette-none.active {
+  box-shadow: 0 0 0 2px #ffffff, 0 0 0 3px rgba(0, 0, 0, 0.4);
+}
+
+.color-palette-grid {
+  display: grid;
+  grid-template-columns: repeat(24, 24px);
+  grid-auto-rows: 24px;
+  gap: 2px;
+}
+
+.color-palette-swatch {
+  width: 24px;
+  height: 24px;
+  border-radius: 5px;
+  cursor: pointer;
+  padding: 0;
+}
+
+.color-palette-swatch:hover {
+  transform: translateY(-1px);
+}
+
+.color-palette-swatch.active {
+  box-shadow: 0 0 0 2px #ffffff, 0 0 0 3px rgba(0, 0, 0, 0.4);
+}

src/components/common/ColorPalettePopup.tsx

@@ -0,0 +1,43 @@
+import React from 'react';
+import { FaUndoAlt } from 'react-icons/fa';
+import { LOGIC_REGION_COLOR_SWATCHES } from '../../constants/regionColorPalette';
+import './ColorPalettePopup.css';
+
+interface ColorPalettePopupProps {
+  selectedColor?: string;
+  onSelect: (color: string | null) => void;
+  className?: string;
+}
+
+const ColorPalettePopup: React.FC<ColorPalettePopupProps> = ({
+  selectedColor,
+  onSelect,
+  className = '',
+}) => (
+  <div className={`color-palette-popup ${className}`.trim()} role="menu" aria-label="Color palette">
+    <button
+      type="button"
+      className={`color-palette-none${selectedColor === undefined ? ' active' : ''}`}
+      onClick={() => onSelect(null)}
+      aria-label="Reset color"
+      title="Reset color"
+    >
+      <FaUndoAlt aria-hidden="true" />
+    </button>
+    <div className="color-palette-grid">
+      {LOGIC_REGION_COLOR_SWATCHES.flat().map((color) => (
+        <button
+          key={color}
+          type="button"
+          className={`color-palette-swatch${selectedColor === color ? ' active' : ''}`}
+          style={{ backgroundColor: color }}
+          onClick={() => onSelect(color)}
+          title={color}
+          aria-label={`Select color ${color}`}
+        />
+      ))}
+    </div>
+  </div>
+);
+
+export default ColorPalettePopup;

src/components/common/index.ts

@@ -1,4 +1,5 @@
 export { default as KGDropdown } from './KGDropdown';
+export { default as ColorPalettePopup } from './ColorPalettePopup';
 export { default as Playhead } from './Playhead';
 export { default as FileImportModal } from './FileImportModal'; 
 export { default as LoadingOverlay } from './LoadingOverlay';

src/components/interfaces.ts

@@ -16,6 +16,10 @@ export interface RegionUI {
   barNumber: number;
   length: number;
   name: string;
+  color?: string;
+  trackColor?: string;
+  effectiveColor?: string;
+  isAudioRegion?: boolean;
 }
 
 export interface RegionPreviewContentStyle {

src/components/piano-roll/PianoRoll.css

@@ -247,6 +247,22 @@
   cursor: default;
 }
 
+.piano-roll-menu-item-wrapper {
+  position: relative;
+}
+
+.piano-roll-more-menu {
+  overflow: visible;
+  max-height: none;
+}
+
+.piano-roll-region-color-popup {
+  position: absolute;
+  top: calc(100% + 6px);
+  right: 0;
+  z-index: 1600;
+}
+
 .piano-roll-automation-toolbar-group {
   display: flex;
   align-items: center;

src/components/piano-roll/PianoRoll.tsx

@@ -101,7 +101,7 @@ const PianoRoll: React.FC<PianoRollProps> = ({
   const isAudioWaveform = currentMode === 'audio-waveform';
   const isAudioOnly = isAudioWaveform || isSpectrogram;
   const isHybrid = currentMode === 'hybrid';
-  const { maxBars, tracks, updateTrack, timeSignature, showChatBox, showKGOnePanel, showEventListPanel, showInstrumentSelection, keySignature, selectedMode, setSelectedMode, playheadPosition, isPlaying, autoScrollEnabled, bpm, pianoRollScrollRequest, selectedNoteIds, automationRedrawVersion, refreshProjectState, setBpm } = useProjectStore();
+  const { maxBars, tracks, updateTrack, updateRegionProperties, timeSignature, showChatBox, showKGOnePanel, showEventListPanel, showInstrumentSelection, keySignature, selectedMode, setSelectedMode, playheadPosition, isPlaying, autoScrollEnabled, bpm, pianoRollScrollRequest, selectedNoteIds, selectedRegionIds, automationRedrawVersion, refreshProjectState, setBpm } = useProjectStore();
   const { t } = useI18n();
 
   // Tool state for piano roll
@@ -167,6 +167,14 @@ const PianoRoll: React.FC<PianoRollProps> = ({
   const activeInstrument = useMemo<InstrumentType>(() => (
     parentMidiTrack instanceof KGMidiTrack ? parentMidiTrack.getInstrument() : 'acoustic_grand_piano'
   ), [parentMidiTrack]);
+  const activeEditableRegionId = audioRegion?.getId() ?? activeRegion?.getId() ?? null;
+  const selectedRegionColor = useMemo(() => {
+    if (audioRegion) {
+      return audioRegion.getColor();
+    }
+
+    return activeRegion?.getColor();
+  }, [activeRegion, audioRegion]);
   const parsedSheetQuantization = useMemo(
     () => parseSheetQuantization(sheetQuantization),
     [sheetQuantization]
@@ -492,6 +500,20 @@ const PianoRoll: React.FC<PianoRollProps> = ({
     }
   };
 
+  const handleRegionColorSelect = useCallback(async (color: string | null) => {
+    const allTrackRegionIds = new Set(tracks.flatMap(track => track.getRegions().map(region => region.getId())));
+    const selectedProjectRegionIds = selectedRegionIds.filter(regionId => allTrackRegionIds.has(regionId));
+    const targetRegionIds = activeEditableRegionId && selectedProjectRegionIds.includes(activeEditableRegionId)
+      ? selectedProjectRegionIds
+      : activeEditableRegionId
+        ? [activeEditableRegionId]
+        : [];
+
+    for (const regionId of targetRegionIds) {
+      await updateRegionProperties(regionId, { color });
+    }
+  }, [activeEditableRegionId, selectedRegionIds, tracks, updateRegionProperties]);
+
   const handleDetectChords = useCallback(async () => {
     if (!audioRegion && !activeRegion) {
       await showAlert('Open a MIDI or audio region before detecting chords.');
@@ -1597,6 +1619,8 @@ const PianoRoll: React.FC<PianoRollProps> = ({
         detectingChords={isDetectingChords}
         onDetectTempo={audioRegion ? handleDetectTempo : undefined}
         detectingTempo={isDetectingTempo}
+        selectedRegionColor={selectedRegionColor}
+        onRegionColorSelect={activeEditableRegionId ? (color) => { void handleRegionColorSelect(color); } : undefined}
       />
 
       <NoteAttributeBar selectedNotes={selectedNotes} isSpectrogram={isAudioOnly} activeRegion={activeRegion} />

src/components/piano-roll/PianoRollToolbar.test.tsx

@@ -30,6 +30,16 @@ vi.mock('../common', () => ({
       </button>
     );
   },
+  ColorPalettePopup: ({ onSelect }: { onSelect: (value: string | null) => void }) => (
+    <div>
+      <button type="button" aria-label="Reset color" onClick={() => onSelect(null)}>
+        Reset
+      </button>
+      <button type="button" onClick={() => onSelect('#3C8AC4')}>
+        Color Swatch
+      </button>
+    </div>
+  ),
 }));
 
 vi.mock('../../core/KGCore', () => ({
@@ -431,4 +441,23 @@ describe('PianoRollToolbar', () => {
 
     expect(screen.getByRole('button', { name: '和声小调' })).toBeInTheDocument();
   });
+
+  it('shows the region color action in the more menu and emits the chosen color', () => {
+    const onRegionColorSelect = vi.fn();
+
+    renderWithLocale(
+      <PianoRollToolbar
+        {...baseProps}
+        mode="midi-edit"
+        onRegionColorSelect={onRegionColorSelect}
+        selectedRegionColor="#3C8AC4"
+      />
+    );
+
+    fireEvent.click(screen.getByRole('button', { name: 'More options' }));
+    fireEvent.click(screen.getByText('Region Color...'));
+    fireEvent.click(screen.getByRole('button', { name: 'Reset color' }));
+
+    expect(onRegionColorSelect).toHaveBeenCalledWith(null);
+  });
 });

src/components/piano-roll/PianoRollToolbar.tsx

@@ -1,7 +1,7 @@
 import React from 'react';
 import { FaMousePointer, FaPencilAlt } from 'react-icons/fa';
 import { TbArrowBarToUp } from 'react-icons/tb';
-import { KGDropdown } from '../common';
+import { ColorPalettePopup, KGDropdown } from '../common';
 import { KGPianoRollState } from '../../core/state/KGPianoRollState';
 import { KGCore } from '../../core/KGCore';
 import {
@@ -50,6 +50,8 @@ interface PianoRollToolbarProps {
   detectingChords?: boolean;
   onDetectTempo?: () => void | Promise<void>;
   detectingTempo?: boolean;
+  selectedRegionColor?: string;
+  onRegionColorSelect?: (color: string | null) => void;
 }
 
 const PianoRollToolbar: React.FC<PianoRollToolbarProps> = ({
@@ -92,6 +94,8 @@ const PianoRollToolbar: React.FC<PianoRollToolbarProps> = ({
   detectingChords = false,
   onDetectTempo,
   detectingTempo = false,
+  selectedRegionColor,
+  onRegionColorSelect,
 }) => {
   const { t } = useI18n();
   const showMidiControls = mode !== 'spectrogram' && mode !== 'audio-waveform' && !sheetMusicViewEnabled;
@@ -151,6 +155,7 @@ const PianoRollToolbar: React.FC<PianoRollToolbarProps> = ({
   }, [showZoomSlider]);
 
   const [showMoreMenu, setShowMoreMenu] = React.useState(false);
+  const [showRegionColorPalette, setShowRegionColorPalette] = React.useState(false);
   const specMenuRef = React.useRef<HTMLDivElement>(null);
 
   React.useEffect(() => {
@@ -158,6 +163,7 @@ const PianoRollToolbar: React.FC<PianoRollToolbarProps> = ({
     const handleClickOutside = (e: MouseEvent) => {
       if (specMenuRef.current && !specMenuRef.current.contains(e.target as Node)) {
         setShowMoreMenu(false);
+        setShowRegionColorPalette(false);
       }
     };
     document.addEventListener('mousedown', handleClickOutside);
@@ -386,7 +392,29 @@ const PianoRollToolbar: React.FC<PianoRollToolbarProps> = ({
               ...
             </button>
             {showMoreMenu && (
-              <div className="quant-dropdown" style={{ right: 0, left: 'auto', width: 'auto', whiteSpace: 'nowrap' }}>
+              <div className="quant-dropdown piano-roll-more-menu" style={{ right: 0, left: 'auto', width: 'auto', whiteSpace: 'nowrap' }}>
+                {onRegionColorSelect && (
+                  <div className="piano-roll-menu-item-wrapper">
+                    <div
+                      className="quant-option"
+                      onClick={() => setShowRegionColorPalette(open => !open)}
+                    >
+                      {t('pianoRoll.regionColor')}
+                    </div>
+                    {showRegionColorPalette && (
+                      <div className="piano-roll-region-color-popup">
+                        <ColorPalettePopup
+                          selectedColor={selectedRegionColor}
+                          onSelect={(color) => {
+                            onRegionColorSelect(color);
+                            setShowRegionColorPalette(false);
+                            setShowMoreMenu(false);
+                          }}
+                        />
+                      </div>
+                    )}
+                  </div>
+                )}
                 {onDetectChords && (
                   <div
                     className={`quant-option${detectingChords ? ' disabled' : ''}`}
@@ -394,6 +422,7 @@ const PianoRollToolbar: React.FC<PianoRollToolbarProps> = ({
                       if (detectingChords) {
                         return;
                       }
+                      setShowRegionColorPalette(false);
                       setShowMoreMenu(false);
                       void onDetectChords();
                     }}
@@ -409,6 +438,7 @@ const PianoRollToolbar: React.FC<PianoRollToolbarProps> = ({
                       if (detectingTempo) {
                         return;
                       }
+                      setShowRegionColorPalette(false);
                       setShowMoreMenu(false);
                       void onDetectTempo();
                     }}

src/components/track/Region.css

@@ -1,8 +1,8 @@
 /* Track Region Styles */
 .track-region {
   position: absolute;
-  background-color: #4a6b8a;
+  background-color: var(--region-header-bg, #4a6b8a);
-  border: 2px solid #5a7b9a;
+  border: 2px solid var(--region-border-color, #5a7b9a);
   border-radius: 3px;
   height: calc(100%);
   margin: 0px;
@@ -48,7 +48,7 @@
 }
 
 .region-header {
-  background-color: #5a7b9a;
+  background-color: var(--region-header-bg, #5a7b9a);
   color: #fff;
   padding: 2px 6px;
   font-size: 11px;
@@ -61,19 +61,19 @@
 }
 
 .track-region:hover .region-header {
-  background-color: #6a8baa;
+  background-color: var(--region-header-hover-bg, #6a8baa);
 }
 
 .region-content {
   height: calc(100% - 18px);
-  background-color: #87CEFA; /* Light blue */
+  background-color: var(--region-content-bg, #4B9A41); /* Default MIDI region color */
   width: 100%;
   position: relative; /* Allow overlayed controls */
   overflow: hidden;
 }
 
 .region-content.audio-region-content {
-  background-color: #90EE90; /* Light green for audio regions */
+  background-color: var(--region-content-bg, #39649E); /* Default audio region color */
 }
 
 .region-preview-content {
@@ -91,8 +91,8 @@
 
 /* Audio region overrides */
 .track-region.audio-region {
-  background-color: #3a6b4a;
+  background-color: var(--region-header-bg, #3a6b4a);
-  border-color: #4a8b5a;
+  border-color: var(--region-border-color, #4a8b5a);
 }
 
 .track-region.audio-region.selected {
@@ -109,11 +109,11 @@
 }
 
 .track-region.audio-region .region-header {
-  background-color: #4a8b5a;
+  background-color: var(--region-header-bg, #4a8b5a);
 }
 
 .track-region.audio-region:hover .region-header {
-  background-color: #5a9b6a;
+  background-color: var(--region-header-hover-bg, #5a9b6a);
 }
 
 /* Left-side button cluster inside region-content */

src/components/track/Track.css

@@ -259,6 +259,49 @@
   color: #101010;
 }
 
+.track-settings-menu {
+  position: absolute;
+  top: 100%;
+  left: 0;
+  z-index: 10000;
+  margin-top: 2px;
+  min-width: 120px;
+  padding: 4px 0;
+  border: 1px solid #444;
+  border-radius: 3px;
+  background: #2d2d2d;
+  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
+}
+
+.track-settings-menu-item {
+  display: flex !important;
+  align-items: center !important;
+  justify-content: flex-start !important;
+  width: 100%;
+  min-width: 120px;
+  height: auto !important;
+  margin: 0 !important;
+  padding: 6px 10px !important;
+  border: none !important;
+  border-radius: 0 !important;
+  background: transparent !important;
+  color: #e0e0e0 !important;
+  font-size: 12px !important;
+  line-height: 1.2 !important;
+  white-space: nowrap;
+}
+
+.track-settings-menu-item:hover {
+  background: #444 !important;
+}
+
+.track-settings-color-popup {
+  position: absolute;
+  top: 0;
+  left: calc(100% + 6px);
+  z-index: 10001;
+}
+
 .track-grid.automation-active {
   position: relative;
 }

src/components/track/TrackGridItem.tsx

@@ -12,6 +12,7 @@ import { useProjectStore } from '../../stores/projectStore';
 import { isModifierKeyPressed } from '../../util/osUtil';
 import { CHORD_REGION_IMPORT_MIME_TYPE } from '../../util/chordRegionImportUtil';
 import { TrackType } from '../../core/track/KGTrack';
+import { buildRegionSurfaceColors, resolveRegionColor } from '../../util/regionColor';
 
 interface RegionResizePreviewBaseline {
   regionId: string;
@@ -795,12 +796,22 @@ const TrackGridItem: React.FC<TrackGridItemProps> = ({
           );
         }
 
+        const effectiveColor = region.effectiveColor
+          ?? resolveRegionColor(coreRegion?.getColor(), track.getColor(), !!audioRegion || !!region.isAudioRegion);
+        const surfaceColors = buildRegionSurfaceColors(effectiveColor);
+
         return (
           <RegionItem
             key={region.id}
             id={region.id}
             name={region.name}
-            style={getRegionStyle(region)}
+            style={{
+              ...getRegionStyle(region),
+              ['--region-border-color' as string]: surfaceColors.borderColor,
+              ['--region-header-bg' as string]: surfaceColors.headerColor,
+              ['--region-header-hover-bg' as string]: surfaceColors.headerHoverColor,
+              ['--region-content-bg' as string]: surfaceColors.contentColor,
+            }}
             barNumber={region.barNumber}
             length={region.length}
             trackIndex={index}

src/components/track/TrackInfoItem.test.tsx

@@ -12,6 +12,7 @@ const storeState = {
   removeTrack: vi.fn(),
   toggleInstrumentSelectionForTrack: vi.fn(),
   importAudioToTrack: vi.fn(),
+  updateTrackProperties: vi.fn(),
   tracks: [] as KGAudioTrack[],
   activeTrackAutomationTrackId: null as string | null,
   activeTrackAutomationType: null as string | null,
@@ -21,8 +22,13 @@ const storeState = {
 let fileImportModalProps: Record<string, unknown> | null = null;
 
 vi.mock('../../stores/projectStore', () => ({
-  useProjectStore: (selector?: (state: typeof storeState) => unknown) => (
+  useProjectStore: Object.assign(
-    selector ? selector(storeState) : storeState
+    (selector?: (state: typeof storeState) => unknown) => (
+      selector ? selector(storeState) : storeState
+    ),
+    {
+      getState: () => storeState,
+    },
   ),
 }));
 
@@ -73,6 +79,7 @@ describe('TrackInfoItem audio import', () => {
     storeState.removeTrack.mockReset();
     storeState.toggleInstrumentSelectionForTrack.mockReset();
     storeState.importAudioToTrack.mockReset();
+    storeState.updateTrackProperties.mockReset();
     storeState.setTrackAutomationView.mockReset();
     vi.mocked(showConfirm).mockReset();
   });
@@ -127,4 +134,32 @@ describe('TrackInfoItem audio import', () => {
       translate('track.controls.settings.deleteTrackConfirm', { name: '钢琴' }, 'zh_cn')
     );
   });
+
+  it('shows the track color entry and clears the color override', async () => {
+    const audioTrack = new KGAudioTrack('Audio Track', 1);
+    audioTrack.setTrackIndex(0);
+    audioTrack.setColor('#3C8AC4');
+    storeState.tracks = [audioTrack];
+    storeState.updateTrackProperties.mockResolvedValue(undefined);
+
+    render(
+      <TrackInfoItem
+        track={audioTrack}
+        index={0}
+        isDragging={false}
+        isDragOver={false}
+        onTrackNameEdit={vi.fn()}
+        onDragStart={vi.fn()}
+        onDragOver={vi.fn()}
+        onDrop={vi.fn()}
+        onDragEnd={vi.fn()}
+      />
+    );
+
+    fireEvent.click(screen.getByRole('button', { name: '更多操作' }));
+    fireEvent.click(screen.getByRole('button', { name: '轨道颜色...' }));
+    fireEvent.click(screen.getByRole('button', { name: 'Reset color' }));
+
+    expect(storeState.updateTrackProperties).toHaveBeenCalledWith(1, { color: null });
+  });
 });

src/components/track/TrackInfoItem.tsx

@@ -7,6 +7,7 @@ import { TbPiano } from 'react-icons/tb';
 import { TbDots } from 'react-icons/tb';
 import { FaFileAudio } from 'react-icons/fa';
 import KGDropdown from '../common/KGDropdown';
+import ColorPalettePopup from '../common/ColorPalettePopup';
 import FileImportModal from '../common/FileImportModal';
 import { FLUIDR3_INSTRUMENT_MAP } from '../../constants/generalMidiConstants';
 import { DEBUG_MODE } from '../../constants/uiConstants';
@@ -91,6 +92,7 @@ const TrackInfoItem: React.FC<TrackInfoItemProps> = ({
   const [showSettingsDropdown, setShowSettingsDropdown] = useState(false);
   const [showAudioImportModal, setShowAudioImportModal] = useState(false);
   const [showAutomationDropdown, setShowAutomationDropdown] = useState(false);
+  const [showTrackColorPalette, setShowTrackColorPalette] = useState(false);
   const settingsDropdownRef = useRef<HTMLDivElement>(null);
   const automationDropdownRef = useRef<HTMLDivElement>(null);
   const suppressDragRef = useRef(false);
@@ -115,6 +117,7 @@ const TrackInfoItem: React.FC<TrackInfoItemProps> = ({
         !settingsDropdownRef.current.contains(event.target as Node)
       ) {
         setShowSettingsDropdown(false);
+        setShowTrackColorPalette(false);
       }
       if (
         showAutomationDropdown &&
@@ -336,6 +339,9 @@ const TrackInfoItem: React.FC<TrackInfoItemProps> = ({
   const handleSettingsButtonClick = (e: React.MouseEvent) => {
     e.stopPropagation();
     setShowSettingsDropdown(!showSettingsDropdown);
+    if (showSettingsDropdown) {
+      setShowTrackColorPalette(false);
+    }
   };
 
   const handleAutomationButtonClick = (e: React.MouseEvent<HTMLButtonElement>) => {
@@ -387,6 +393,17 @@ const TrackInfoItem: React.FC<TrackInfoItemProps> = ({
     }
   };
 
+  const handleTrackColorSelect = async (color: string | null) => {
+    try {
+      await useProjectStore.getState().updateTrackProperties(track.getId(), { color });
+    } catch (error) {
+      console.error('Failed to update track color:', error);
+    } finally {
+      setShowTrackColorPalette(false);
+      setShowSettingsDropdown(false);
+    }
+  };
+
   return (
     <div 
       className={`track-info ${isDragOver ? 'drag-over' : ''} ${isDragging ? 'dragging' : ''} ${isSelected ? 'selected' : ''}`}
@@ -545,18 +562,38 @@ const TrackInfoItem: React.FC<TrackInfoItemProps> = ({
             >
               <TbDots />
             </button>
-            <div style={{ position: 'absolute', top: '100%', left: 0, zIndex: 10000 }}>
+            {showSettingsDropdown && (
-              <KGDropdown
+              <div className="track-settings-menu">
-                options={[{ label: t('track.controls.settings.deleteTrack'), value: 'Delete Track' }]}
+                <button
-                value={''}
+                  type="button"
-                onChange={handleSettingsAction}
+                  className="track-settings-menu-item"
-                label={t('track.controls.moreActions')}
+                  onClick={(e) => {
-                hideButton={true}
+                    e.stopPropagation();
-                isOpen={showSettingsDropdown}
+                    setShowTrackColorPalette((open) => !open);
-                onToggle={setShowSettingsDropdown}
+                  }}
-                className="settings-dropdown"
+                >
-              />
+                  {t('track.controls.settings.trackColor')}
-            </div>
+                </button>
+                <button
+                  type="button"
+                  className="track-settings-menu-item"
+                  onClick={(e) => {
+                    e.stopPropagation();
+                    void handleSettingsAction('Delete Track');
+                  }}
+                >
+                  {t('track.controls.settings.deleteTrack')}
+                </button>
+                {showTrackColorPalette && (
+                  <div className="track-settings-color-popup">
+                    <ColorPalettePopup
+                      selectedColor={track.getColor()}
+                      onSelect={handleTrackColorSelect}
+                    />
+                  </div>
+                )}
+              </div>
+            )}
           </div>
         </div>
       </div>

src/constants/regionColorPalette.ts

@@ -0,0 +1,11 @@
+export const DEFAULT_MIDI_REGION_COLOR = '#4B9A41';
+export const DEFAULT_AUDIO_REGION_COLOR = '#39649E';
+
+export const LOGIC_REGION_COLOR_SWATCHES: readonly string[][] = [
+  ['#B43F1D', '#B65720', '#B97423', '#BE9B2A', '#C3C031', '#A2BF30', '#84BE2E', '#6BBD2D', '#4EBC3A', '#4EBD58', '#4DBD78', '#4DBE9B', '#4CBEC2', '#3C99C0', '#3C8AC4', '#3D77C9', '#3B5ECC', '#3A43CE', '#4E41CA', '#643EC8', '#7A38C6', '#8D2EBE', '#B233BD', '#B33097'],
+  ['#8E3A1F', '#904C21', '#926124', '#957C27', '#9A972C', '#82962B', '#6C952A', '#599529', '#409435', '#40954D', '#409564', '#3F957D', '#3F9698', '#347B97', '#367099', '#39649E', '#3852A0', '#383EA2', '#463CA0', '#55389D', '#67359D', '#722995', '#8C2D96', '#8C2B7A'],
+  ['#69331E', '#6B3E20', '#6D4C22', '#706025', '#717126', '#627026', '#546F25', '#476F26', '#336F2E', '#336F3F', '#336E4F', '#337060', '#327070', '#2C5E70', '#2F5672', '#324F75', '#314476', '#323576', '#3B3476', '#463375', '#4F3073', '#57256F', '#68266F', '#69275E'],
+  ['#48271B', '#492F1C', '#4A381D', '#4C421F', '#4D4C1F', '#444C1E', '#3C4C1E', '#344B1F', '#264B24', '#264B2E', '#264B38', '#274B42', '#264B4C', '#23414B', '#263E4D', '#293A50', '#27324F', '#28294F', '#2E294F', '#342850', '#38254D', '#3D1F4A', '#47204B', '#481F41'],
+] as const;
+
+export const LOGIC_REGION_COLOR_OPTIONS: readonly string[] = LOGIC_REGION_COLOR_SWATCHES.flat();

src/core/KGCore.ts

@@ -5,6 +5,7 @@ import { ConfigManager } from './config/ConfigManager';
 import { KGProjectStorage } from './io/KGProjectStorage';
 import { KGConfigUpgrader } from './config-upgrader/KGConfigUpgrader';
 import { KGMidiRegion } from './region/KGMidiRegion';
+import { KGAudioRegion } from './region/KGAudioRegion';
 import { KGMidiNote } from './midi/KGMidiNote';
 import { KGMidiControllerEvent } from './midi/KGMidiControllerEvent';
 import { KGMidiPitchBend } from './midi/KGMidiPitchBend';
@@ -535,6 +536,7 @@ export class KGCore {
             region.getStartFromBeat(),
             region.getLength()
           );
+          clonedRegion.setColor(region.getColor());
           
           // Copy all notes within the region
           const originalNotes = region.getNotes();
@@ -569,6 +571,25 @@ export class KGCore {
           break;
         }
 
+        case 'KGAudioRegion': {
+          const region = item as KGAudioRegion;
+          const clonedRegion = new KGAudioRegion(
+            generateUniqueId('KGAudioRegion'),
+            region.getTrackId(),
+            region.getTrackIndex(),
+            region.getName(),
+            region.getStartFromBeat(),
+            region.getLength(),
+            region.getAudioFileId(),
+            region.getAudioFileName(),
+            region.getAudioDurationSeconds(),
+            region.getClipStartOffsetSeconds()
+          );
+          clonedRegion.setColor(region.getColor());
+          clonedItems.push(clonedRegion);
+          break;
+        }
+        
         case 'KGRegion': {
           const region = item as KGRegion;
           const clonedRegion = new KGRegion(
@@ -579,6 +600,7 @@ export class KGCore {
             region.getStartFromBeat(),
             region.getLength()
           );
+          clonedRegion.setColor(region.getColor());
           clonedItems.push(clonedRegion);
           break;
         }

src/core/commands/region/PasteRegionsCommand.ts

@@ -8,6 +8,7 @@ import { KGMidiPitchBend } from '../../midi/KGMidiPitchBend';
 import { KGTrack } from '../../track/KGTrack';
 import { generateUniqueId } from '../../../util/miscUtil';
 import { useProjectStore } from '../../../stores/projectStore';
+import { KGAudioRegion } from '../../region/KGAudioRegion';
 
 /**
  * Command to paste regions with their notes to a target track at a specific position
@@ -71,6 +72,7 @@ export class PasteRegionsCommand extends KGCommand {
           newPosition,
           originalRegion.getLength()
         );
+        newRegion.setColor(originalRegion.getColor());
         
         // Copy all notes from the original region
         const originalNotes = originalRegion.getNotes();
@@ -102,6 +104,22 @@ export class PasteRegionsCommand extends KGCommand {
         });
         
         console.log(`Created MIDI region "${newRegion.getName()}" with ${originalNotes.length} notes`);
+      } else if (originalRegion instanceof KGAudioRegion) {
+        newRegion = new KGAudioRegion(
+          generateUniqueId('KGAudioRegion'),
+          targetTrack.getId().toString(),
+          targetTrack.getTrackIndex(),
+          `${originalRegion.getName()} (Copy)`,
+          newPosition,
+          originalRegion.getLength(),
+          originalRegion.getAudioFileId(),
+          originalRegion.getAudioFileName(),
+          originalRegion.getAudioDurationSeconds(),
+          originalRegion.getClipStartOffsetSeconds()
+        );
+        newRegion.setColor(originalRegion.getColor());
+
+        console.log(`Created audio region "${newRegion.getName()}"`);
       } else {
         // Fallback for other region types
         newRegion = new KGRegion(
@@ -112,6 +130,7 @@ export class PasteRegionsCommand extends KGCommand {
           newPosition,
           originalRegion.getLength()
         );
+        newRegion.setColor(originalRegion.getColor());
         
         console.log(`Created region "${newRegion.getName()}"`);
       }

src/core/commands/region/SplitRegionCommand.ts

@@ -93,6 +93,8 @@ export class SplitRegionCommand extends KGCommand {
         this.splitAtBeat,
         regionLength - splitOffsetBeats
       );
+      region1.setColor(originalRegion.getColor());
+      region2.setColor(originalRegion.getColor());
 
       for (const note of originalRegion.getNotes()) {
         if (note.getStartBeat() < splitOffsetBeats) {
@@ -167,6 +169,7 @@ export class SplitRegionCommand extends KGCommand {
         originalRegion.getAudioDurationSeconds(),
         originalRegion.getClipStartOffsetSeconds()
       );
+      this.region1.setColor(originalRegion.getColor());
 
       this.region2 = new KGAudioRegion(
         generateUniqueId('KGAudioRegion'),
@@ -180,6 +183,7 @@ export class SplitRegionCommand extends KGCommand {
         originalRegion.getAudioDurationSeconds(),
         originalRegion.getClipStartOffsetSeconds() + splitOffsetSeconds
       );
+      this.region2.setColor(originalRegion.getColor());
 
     } else {
       throw new Error(`Unsupported region type for splitting: ${originalRegion.getCurrentType()}`);

src/core/commands/region/UpdateRegionCommand.test.ts

@@ -0,0 +1,54 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { KGCore } from '../../KGCore';
+import { KGProject } from '../../KGProject';
+import { KGTrack } from '../../track/KGTrack';
+import { KGMidiRegion } from '../../region/KGMidiRegion';
+import { UpdateRegionCommand } from './UpdateRegionCommand';
+
+vi.mock('../../KGCore', () => ({
+  KGCore: {
+    instance: vi.fn(),
+  },
+}));
+
+describe('UpdateRegionCommand', () => {
+  let track: KGTrack;
+  let region: KGMidiRegion;
+  let project: KGProject;
+  const mockCore = {
+    getCurrentProject: vi.fn(),
+  };
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    track = new KGTrack('Track 1', 1);
+    region = new KGMidiRegion('region-1', '1', 0, 'Verse', 0, 4);
+    track.setRegions([region]);
+    project = new KGProject('Test', 32, 0, 125, undefined, undefined, undefined, undefined, undefined, 1, [track], 11);
+    mockCore.getCurrentProject.mockReturnValue(project);
+    vi.mocked(KGCore.instance).mockReturnValue(mockCore as unknown as KGCore);
+  });
+
+  it('updates color and restores it on undo', () => {
+    const command = new UpdateRegionCommand('region-1', { color: '#3D77C9' });
+
+    command.execute();
+
+    expect(region.getColor()).toBe('#3D77C9');
+    expect(command.getChangedProperties()).toEqual(new Set(['color']));
+
+    command.undo();
+
+    expect(region.getColor()).toBeUndefined();
+  });
+
+  it('clears an existing region color override', () => {
+    region.setColor('#B43F1D');
+    const command = new UpdateRegionCommand('region-1', { color: null });
+
+    command.execute();
+
+    expect(region.getColor()).toBeUndefined();
+    expect(command.getChangedProperties()).toEqual(new Set(['color']));
+  });
+});

src/core/commands/region/UpdateRegionCommand.ts

@@ -8,7 +8,7 @@ import { KGTrack } from '../../track/KGTrack';
  */
 export interface RegionUpdateProperties {
   name?: string;
-  // Future properties can be added here (e.g., color, instrument, etc.)
+  color?: string | null;
 }
 
 /**
@@ -58,6 +58,7 @@ export class UpdateRegionCommand extends KGCommand {
     // Store original properties for undo
     this.originalProperties = {
       name: this.targetRegion.getName(),
+      color: this.targetRegion.getColor(),
     };
 
     // Apply updates and track what actually changes
@@ -70,6 +71,12 @@ export class UpdateRegionCommand extends KGCommand {
       updatedProperties.push(`name: "${this.originalProperties.name}" → "${this.newProperties.name}"`);
     }
 
+    if ('color' in this.newProperties && this.newProperties.color !== this.originalProperties.color) {
+      this.targetRegion.setColor(this.newProperties.color ?? undefined);
+      this.changedProperties.add('color');
+      updatedProperties.push(`color: ${this.originalProperties.color ?? 'none'} → ${this.newProperties.color ?? 'none'}`);
+    }
+
     if (updatedProperties.length > 0) {
       console.log(`Updated region ${this.regionId}: ${updatedProperties.join(', ')}`);
     } else {
@@ -91,6 +98,11 @@ export class UpdateRegionCommand extends KGCommand {
       restoredProperties.push(`name: "${this.originalProperties.name}"`);
     }
 
+    if (this.changedProperties.has('color')) {
+      this.targetRegion.setColor(this.originalProperties.color ?? undefined);
+      restoredProperties.push(`color: ${this.originalProperties.color ?? 'none'}`);
+    }
+
     console.log(`Restored region ${this.regionId}: ${restoredProperties.join(', ')}`);
   }
 
@@ -101,6 +113,9 @@ export class UpdateRegionCommand extends KGCommand {
     if (this.newProperties.name !== undefined) {
       updatedProps.push('name');
     }
+    if ('color' in this.newProperties) {
+      updatedProps.push('color');
+    }
 
     if (updatedProps.length === 1) {
       return `Update region "${regionName}" ${updatedProps[0]}`;

src/core/commands/track/UpdateTrackCommand.test.ts

@@ -84,4 +84,27 @@ describe('UpdateTrackCommand', () => {
     expect(mockAudioInterface.setTrackSolo).not.toHaveBeenCalled();
     expect(command.getChangedProperties()).toEqual(new Set());
   });
+
+  it('updates color and restores it on undo', () => {
+    const command = new UpdateTrackCommand(1, { color: '#3C8AC4' });
+
+    command.execute();
+
+    expect(track.getColor()).toBe('#3C8AC4');
+    expect(command.getChangedProperties()).toEqual(new Set(['color']));
+
+    command.undo();
+
+    expect(track.getColor()).toBeUndefined();
+  });
+
+  it('clears an existing color override', () => {
+    track.setColor('#B43F1D');
+    const command = new UpdateTrackCommand(1, { color: null });
+
+    command.execute();
+
+    expect(track.getColor()).toBeUndefined();
+    expect(command.getChangedProperties()).toEqual(new Set(['color']));
+  });
 });

src/core/commands/track/UpdateTrackCommand.ts

@@ -14,6 +14,7 @@ export interface TrackUpdateProperties {
   volume?: number;
   muted?: boolean;
   solo?: boolean;
+  color?: string | null;
 }
 
 /**
@@ -51,6 +52,7 @@ export class UpdateTrackCommand extends KGCommand {
       volume: this.targetTrack.getVolume(),
       muted: this.targetTrack.getMuted(),
       solo: this.targetTrack.getSolo(),
+      color: this.targetTrack.getColor(),
     };
 
     // Store original instrument if it's a MIDI track
@@ -133,6 +135,16 @@ export class UpdateTrackCommand extends KGCommand {
       updatedProperties.push(`solo: ${originalSolo} → ${newSolo}`);
     }
 
+    if ('color' in this.newProperties && this.newProperties.color !== this.originalProperties.color) {
+      const newColor = this.newProperties.color ?? undefined;
+      const originalColor = this.originalProperties.color;
+
+      this.targetTrack.setColor(newColor);
+
+      this.changedProperties.add('color');
+      updatedProperties.push(`color: ${originalColor ?? 'none'} → ${newColor}`);
+    }
+
     if (updatedProperties.length > 0) {
       console.log(`Updated track ${this.trackId}: ${updatedProperties.join(', ')}`);
     } else {
@@ -204,6 +216,11 @@ export class UpdateTrackCommand extends KGCommand {
       restoredProperties.push(`solo: ${this.originalProperties.solo}`);
     }
 
+    if (this.changedProperties.has('color')) {
+      this.targetTrack.setColor(this.originalProperties.color ?? undefined);
+      restoredProperties.push(`color: ${this.originalProperties.color ?? 'none'}`);
+    }
+
     console.log(`Restored track ${this.trackId}: ${restoredProperties.join(', ')}`);
   }
 
@@ -229,6 +246,9 @@ export class UpdateTrackCommand extends KGCommand {
     if (this.newProperties.solo !== undefined) {
       updatedProps.push('solo');
     }
+    if ('color' in this.newProperties) {
+      updatedProps.push('color');
+    }
 
     if (updatedProps.length === 1) {
       return `Update track "${trackName}" ${updatedProps[0]}`;

src/core/region/KGRegion.ts

@@ -27,6 +27,9 @@ export class KGRegion implements Selectable {
   @Expose()
   protected length: number = 0;
 
+  @Expose()
+  protected color?: string;
+
   @Expose()
   protected selected: boolean = false;
 
@@ -66,6 +69,10 @@ export class KGRegion implements Selectable {
     return this.length;
   }
 
+  public getColor(): string | undefined {
+    return this.color;
+  }
+
   // Setters
   public setId(id: string): void {
     this.id = id;
@@ -91,6 +98,10 @@ export class KGRegion implements Selectable {
     this.length = length;
   }
 
+  public setColor(color: string | undefined): void {
+    this.color = color;
+  }
+
   // interface methods
   public select(): void {
     this.selected = true;

src/core/track/KGTrack.ts

@@ -34,6 +34,9 @@ export class KGTrack {
   @Expose()
   protected type: TrackType;
 
+  @Expose()
+  protected color?: string;
+
   @Expose()
   @WithDefault(AUDIO_INTERFACE_CONSTANTS.DEFAULT_TRACK_VOLUME)
   protected volume: number = AUDIO_INTERFACE_CONSTANTS.DEFAULT_TRACK_VOLUME;
@@ -99,6 +102,10 @@ export class KGTrack {
     return this.volume;
   }
 
+  public getColor(): string | undefined {
+    return this.color;
+  }
+
   public getMuted(): boolean {
     return this.muted;
   }
@@ -136,6 +143,10 @@ export class KGTrack {
     );
   }
 
+  public setColor(color: string | undefined): void {
+    this.color = color;
+  }
+
   public setMuted(muted: boolean): void {
     this.muted = muted;
   }

src/hooks/useMainContentRegions.ts

@@ -15,6 +15,7 @@ import { DEBUG_MODE } from '../constants';
 import { useProjectStore } from '../stores/projectStore';
 import { useRegionOperations } from './useRegionOperations';
 import { getAudioRegionDisplayLengthBeats } from '../util/globalTrackUtil';
+import { resolveRegionColor } from '../util/regionColor';
 
 const DEFAULT_REGION_CLICK_OPTIONS: RegionClickOptions = {
   shiftKey: false,
@@ -179,6 +180,10 @@ export function useMainContentRegions({
             barNumber,
             length,
             name: region.getName(),
+            color: region.getColor(),
+            trackColor: track.getColor(),
+            effectiveColor: resolveRegionColor(region.getColor(), track.getColor(), region instanceof KGAudioRegion),
+            isAudioRegion: region instanceof KGAudioRegion,
           });
         }
       });

src/i18n/messages/en_us.ts

@@ -327,6 +327,7 @@ export const enUsMessages: TranslationMessages = {
   'pianoRoll.curve': 'Curve',
   'pianoRoll.zoom': 'Zoom',
   'pianoRoll.moreOptions': 'More options',
+  'pianoRoll.regionColor': 'Region Color...',
   'pianoRoll.quantize.1/1': '1/1',
   'pianoRoll.quantize.1/2': '1/2',
   'pianoRoll.quantize.1/3': '1/3',
@@ -538,6 +539,7 @@ export const enUsMessages: TranslationMessages = {
   'track.controls.automation.volume': 'Volume',
   'track.controls.automation.pan': 'Pan',
   'track.controls.moreActions': 'More actions',
+  'track.controls.settings.trackColor': 'Track Color...',
   'track.controls.settings.deleteTrack': 'Delete Track',
   'track.controls.settings.deleteTrackConfirm': 'Are you sure you want to delete track "{name}"?',
   'track.controls.settings.deleteTrackError': 'Failed to delete track. Please try again.',

src/i18n/messages/fr_fr.ts

@@ -315,6 +315,7 @@ export const frFrMessages: TranslationMessages = {
   'pianoRoll.curve': 'Courbe',
   'pianoRoll.zoom': 'Zoom',
   'pianoRoll.moreOptions': 'Plus d\'options',
+  'pianoRoll.regionColor': 'Couleur de la région...',
   'pianoRoll.showActiveRegionOnly': 'Afficher seulement la région active',
   'pianoRoll.showEntireTrack': 'Afficher toute la piste',
   'pianoRoll.detectChords': 'Détecter les accords...',
@@ -422,6 +423,7 @@ export const frFrMessages: TranslationMessages = {
   'track.controls.automation.volume': 'Volume',
   'track.controls.automation.pan': 'Panoramique',
   'track.controls.moreActions': 'Autres actions',
+  'track.controls.settings.trackColor': 'Couleur de la piste...',
   'track.controls.settings.deleteTrack': 'Supprimer la piste',
   'track.controls.settings.deleteTrackConfirm': 'Voulez-vous vraiment supprimer la piste « {name} » ?',
   'track.controls.settings.deleteTrackError': 'Impossible de supprimer la piste. Veuillez réessayer.',

src/i18n/messages/zh_cn.ts

@@ -325,6 +325,7 @@ export const zhCnMessages: TranslationMessages = {
   'pianoRoll.curve': '曲线',
   'pianoRoll.zoom': '缩放',
   'pianoRoll.moreOptions': '更多选项',
+  'pianoRoll.regionColor': '区域颜色...',
   'pianoRoll.quantize.1/1': '1/1',
   'pianoRoll.quantize.1/2': '1/2',
   'pianoRoll.quantize.1/3': '1/3',
@@ -536,6 +537,7 @@ export const zhCnMessages: TranslationMessages = {
   'track.controls.automation.volume': '音量',
   'track.controls.automation.pan': '声像',
   'track.controls.moreActions': '更多操作',
+  'track.controls.settings.trackColor': '轨道颜色...',
   'track.controls.settings.deleteTrack': '删除轨道',
   'track.controls.settings.deleteTrackConfirm': '确定要删除轨道“{name}”吗？',
   'track.controls.settings.deleteTrackError': '删除轨道失败。请重试。',

src/i18n/messages/zh_hk.ts

@@ -325,6 +325,7 @@ export const zhHkMessages: TranslationMessages = {
   'pianoRoll.curve': '曲線',
   'pianoRoll.zoom': '縮放',
   'pianoRoll.moreOptions': '更多選項',
+  'pianoRoll.regionColor': '區域顏色...',
   'pianoRoll.quantize.1/1': '1/1',
   'pianoRoll.quantize.1/2': '1/2',
   'pianoRoll.quantize.1/3': '1/3',
@@ -536,6 +537,7 @@ export const zhHkMessages: TranslationMessages = {
   'track.controls.automation.volume': '音量',
   'track.controls.automation.pan': '聲像',
   'track.controls.moreActions': '更多操作',
+  'track.controls.settings.trackColor': '音軌顏色...',
   'track.controls.settings.deleteTrack': '刪除音軌',
   'track.controls.settings.deleteTrackConfirm': '確定要刪除音軌「{name}」嗎？',
   'track.controls.settings.deleteTrackError': '刪除音軌失敗。請再試一次。',

src/stores/projectStore.ts

@@ -11,7 +11,7 @@ import { KGPianoRollState } from '../core/state/KGPianoRollState';
 import { KGMidiNote } from '../core/midi/KGMidiNote';
 import { KGMidiControllerEvent } from '../core/midi/KGMidiControllerEvent';
 import { KGRegion } from '../core/region/KGRegion';
-import { AddTrackCommand, AddAudioTrackCommand, RemoveTrackCommand, ReorderTracksCommand, UpdateTrackCommand, type TrackUpdateProperties, PasteRegionsCommand, PasteNotesCommand, ChangeProjectPropertyCommand, ImportAudioCommand } from '../core/commands';
+import { AddTrackCommand, AddAudioTrackCommand, RemoveTrackCommand, ReorderTracksCommand, UpdateTrackCommand, type TrackUpdateProperties, PasteRegionsCommand, PasteNotesCommand, ChangeProjectPropertyCommand, ImportAudioCommand, UpdateRegionCommand, type RegionUpdateProperties } from '../core/commands';
 import { KGAudioTrack } from '../core/track/KGAudioTrack';
 import { KGAudioRegion } from '../core/region/KGAudioRegion';
 import { KGAudioFileStorage } from '../core/io/KGAudioFileStorage';
@@ -183,6 +183,7 @@ interface ProjectState {
   removeTrack: (id: number) => Promise<void>;
   updateTrack: (track: KGTrack) => Promise<void>;
   updateTrackProperties: (trackId: number, properties: TrackUpdateProperties) => Promise<void>;
+  updateRegionProperties: (regionId: string, properties: RegionUpdateProperties) => Promise<void>;
   setTrackInstrument: (trackId: number, instrument: InstrumentType) => Promise<void>;
   reorderTracks: (sourceIndex: number, destinationIndex: number) => void;
   setStatus: (status: string) => void;
@@ -856,6 +857,24 @@ export const useProjectStore = create<ProjectState>((set, get) => {
       }
     },
 
+    updateRegionProperties: async (regionId: string, properties: RegionUpdateProperties) => {
+      try {
+        const command = new UpdateRegionCommand(regionId, properties);
+        KGCore.instance().executeCommand(command);
+
+        const project = KGCore.instance().getCurrentProject();
+        set({
+          tracks: [...project.getTracks()] as KGTrack[],
+          globalTracks: [...getProjectGlobalTracks(project)],
+        });
+
+        console.log(`Updated region ${regionId} properties`);
+      } catch (error) {
+        console.error('Error updating region properties:', error);
+        get().setStatus('Failed to update region properties');
+      }
+    },
+
     setTrackInstrument: async (trackId: number, instrument: InstrumentType) => {
       try {
         // Use the new updateTrackProperties method with command pattern

src/util/regionColor.test.ts

@@ -0,0 +1,29 @@
+import { describe, expect, it } from 'vitest';
+import {
+  DEFAULT_AUDIO_REGION_COLOR,
+  DEFAULT_MIDI_REGION_COLOR,
+} from '../constants/regionColorPalette';
+import { buildRegionSurfaceColors, resolveRegionColor } from './regionColor';
+
+describe('regionColor helpers', () => {
+  it('prefers the region color over the track color', () => {
+    expect(resolveRegionColor('#123456', '#654321', false)).toBe('#123456');
+  });
+
+  it('falls back to the track color when the region color is missing', () => {
+    expect(resolveRegionColor(undefined, '#654321', false)).toBe('#654321');
+  });
+
+  it('falls back to the default type color when no overrides are present', () => {
+    expect(resolveRegionColor(undefined, undefined, false)).toBe(DEFAULT_MIDI_REGION_COLOR);
+    expect(resolveRegionColor(undefined, undefined, true)).toBe(DEFAULT_AUDIO_REGION_COLOR);
+  });
+
+  it('builds distinct surface colors for region chrome', () => {
+    const colors = buildRegionSurfaceColors('#4CBEC2');
+
+    expect(colors.borderColor).not.toBe('#4CBEC2');
+    expect(colors.headerColor).not.toBe('#4CBEC2');
+    expect(colors.contentColor).not.toBe('#4CBEC2');
+  });
+});

src/util/regionColor.ts

@@ -0,0 +1,83 @@
+import {
+  DEFAULT_AUDIO_REGION_COLOR,
+  DEFAULT_MIDI_REGION_COLOR,
+} from '../constants/regionColorPalette';
+
+function clampChannel(value: number): number {
+  return Math.max(0, Math.min(255, Math.round(value)));
+}
+
+function normalizeHex(color: string): string {
+  const trimmed = color.trim();
+  const hex = trimmed.startsWith('#') ? trimmed.slice(1) : trimmed;
+  if (hex.length === 3) {
+    return `#${hex.split('').map(channel => channel + channel).join('').toUpperCase()}`;
+  }
+  return `#${hex.toUpperCase()}`;
+}
+
+function parseHexColor(color: string): [number, number, number] | null {
+  const normalized = normalizeHex(color);
+  if (!/^#[0-9A-F]{6}$/.test(normalized)) {
+    return null;
+  }
+
+  return [
+    parseInt(normalized.slice(1, 3), 16),
+    parseInt(normalized.slice(3, 5), 16),
+    parseInt(normalized.slice(5, 7), 16),
+  ];
+}
+
+function rgbToHex(red: number, green: number, blue: number): string {
+  return `#${[red, green, blue].map(channel => clampChannel(channel).toString(16).padStart(2, '0')).join('').toUpperCase()}`;
+}
+
+function mixColor(color: string, target: [number, number, number], amount: number): string {
+  const rgb = parseHexColor(color);
+  if (!rgb) {
+    return color;
+  }
+
+  return rgbToHex(
+    rgb[0] + (target[0] - rgb[0]) * amount,
+    rgb[1] + (target[1] - rgb[1]) * amount,
+    rgb[2] + (target[2] - rgb[2]) * amount,
+  );
+}
+
+export function normalizeRegionColor(color: string | undefined): string | undefined {
+  if (!color) {
+    return undefined;
+  }
+
+  const normalized = normalizeHex(color);
+  return /^#[0-9A-F]{6}$/.test(normalized) ? normalized : undefined;
+}
+
+export function resolveRegionColor(
+  regionColor: string | undefined,
+  trackColor: string | undefined,
+  isAudioRegion: boolean,
+): string {
+  return normalizeRegionColor(regionColor)
+    ?? normalizeRegionColor(trackColor)
+    ?? (isAudioRegion ? DEFAULT_AUDIO_REGION_COLOR : DEFAULT_MIDI_REGION_COLOR);
+}
+
+export function darkenRegionColor(color: string, amount: number): string {
+  return mixColor(color, [0, 0, 0], amount);
+}
+
+export function lightenRegionColor(color: string, amount: number): string {
+  return mixColor(color, [255, 255, 255], amount);
+}
+
+export function buildRegionSurfaceColors(color: string) {
+  return {
+    borderColor: darkenRegionColor(color, 0.35),
+    headerColor: darkenRegionColor(color, 0.2),
+    headerHoverColor: darkenRegionColor(color, 0.1),
+    contentColor: lightenRegionColor(color, 0.06),
+  };
+}