diff --git a/package.json b/package.json
index e39d9fe..cd04b89 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "opencode-theme-editor",
   "private": true,
-  "version": "1.2.0",
+  "version": "1.2.1",
   "type": "module",
   "scripts": {
     "dev": "vite",
diff --git a/public/import-export.sh b/public/import-export.sh
index fd9c745..9491aba 100644
--- a/public/import-export.sh
+++ b/public/import-export.sh
@@ -340,13 +340,169 @@ def parse_alpha(value: str) -> int:
 
 RGBA_PATTERN = re.compile(r'^rgba?\((.+)\)$', re.IGNORECASE)
 
+COLOR_NAME_HEX = {
+    'aliceblue': '#f0f8ff',
+    'antiquewhite': '#faebd7',
+    'aqua': '#00ffff',
+    'aquamarine': '#7fffd4',
+    'azure': '#f0ffff',
+    'beige': '#f5f5dc',
+    'bisque': '#ffe4c4',
+    'black': '#000000',
+    'blanchedalmond': '#ffebcd',
+    'blue': '#0000ff',
+    'blueviolet': '#8a2be2',
+    'brown': '#a52a2a',
+    'burlywood': '#deb887',
+    'cadetblue': '#5f9ea0',
+    'chartreuse': '#7fff00',
+    'chocolate': '#d2691e',
+    'coral': '#ff7f50',
+    'cornflowerblue': '#6495ed',
+    'cornsilk': '#fff8dc',
+    'crimson': '#dc143c',
+    'cyan': '#00ffff',
+    'darkblue': '#00008b',
+    'darkcyan': '#008b8b',
+    'darkgoldenrod': '#b8860b',
+    'darkgray': '#a9a9a9',
+    'darkgreen': '#006400',
+    'darkgrey': '#a9a9a9',
+    'darkkhaki': '#bdb76b',
+    'darkmagenta': '#8b008b',
+    'darkolivegreen': '#556b2f',
+    'darkorange': '#ff8c00',
+    'darkorchid': '#9932cc',
+    'darkred': '#8b0000',
+    'darksalmon': '#e9967a',
+    'darkseagreen': '#8fbc8f',
+    'darkslateblue': '#483d8b',
+    'darkslategray': '#2f4f4f',
+    'darkslategrey': '#2f4f4f',
+    'darkturquoise': '#00ced1',
+    'darkviolet': '#9400d3',
+    'deeppink': '#ff1493',
+    'deepskyblue': '#00bfff',
+    'dimgray': '#696969',
+    'dimgrey': '#696969',
+    'dodgerblue': '#1e90ff',
+    'firebrick': '#b22222',
+    'floralwhite': '#fffaf0',
+    'forestgreen': '#228b22',
+    'fuchsia': '#ff00ff',
+    'gainsboro': '#dcdcdc',
+    'ghostwhite': '#f8f8ff',
+    'gold': '#ffd700',
+    'goldenrod': '#daa520',
+    'gray': '#808080',
+    'green': '#008000',
+    'greenyellow': '#adff2f',
+    'grey': '#808080',
+    'honeydew': '#f0fff0',
+    'hotpink': '#ff69b4',
+    'indianred': '#cd5c5c',
+    'indigo': '#4b0082',
+    'ivory': '#fffff0',
+    'khaki': '#f0e68c',
+    'lavender': '#e6e6fa',
+    'lavenderblush': '#fff0f5',
+    'lawngreen': '#7cfc00',
+    'lemonchiffon': '#fffacd',
+    'lightblue': '#add8e6',
+    'lightcoral': '#f08080',
+    'lightcyan': '#e0ffff',
+    'lightgoldenrodyellow': '#fafad2',
+    'lightgray': '#d3d3d3',
+    'lightgreen': '#90ee90',
+    'lightgrey': '#d3d3d3',
+    'lightpink': '#ffb6c1',
+    'lightsalmon': '#ffa07a',
+    'lightseagreen': '#20b2aa',
+    'lightskyblue': '#87cefa',
+    'lightslategray': '#778899',
+    'lightslategrey': '#778899',
+    'lightsteelblue': '#b0c4de',
+    'lightyellow': '#ffffe0',
+    'lime': '#00ff00',
+    'limegreen': '#32cd32',
+    'linen': '#faf0e6',
+    'magenta': '#ff00ff',
+    'maroon': '#800000',
+    'mediumaquamarine': '#66cdaa',
+    'mediumblue': '#0000cd',
+    'mediumorchid': '#ba55d3',
+    'mediumpurple': '#9370db',
+    'mediumseagreen': '#3cb371',
+    'mediumslateblue': '#7b68ee',
+    'mediumspringgreen': '#00fa9a',
+    'mediumturquoise': '#48d1cc',
+    'mediumvioletred': '#c71585',
+    'midnightblue': '#191970',
+    'mintcream': '#f5fffa',
+    'mistyrose': '#ffe4e1',
+    'moccasin': '#ffe4b5',
+    'navajowhite': '#ffdead',
+    'navy': '#000080',
+    'oldlace': '#fdf5e6',
+    'olive': '#808000',
+    'olivedrab': '#6b8e23',
+    'orange': '#ffa500',
+    'orangered': '#ff4500',
+    'orchid': '#da70d6',
+    'palegoldenrod': '#eee8aa',
+    'palegreen': '#98fb98',
+    'paleturquoise': '#afeeee',
+    'palevioletred': '#db7093',
+    'papayawhip': '#ffefd5',
+    'peachpuff': '#ffdab9',
+    'peru': '#cd853f',
+    'pink': '#ffc0cb',
+    'plum': '#dda0dd',
+    'powderblue': '#b0e0e6',
+    'purple': '#800080',
+    'rebeccapurple': '#663399',
+    'red': '#ff0000',
+    'rosybrown': '#bc8f8f',
+    'royalblue': '#4169e1',
+    'saddlebrown': '#8b4513',
+    'salmon': '#fa8072',
+    'sandybrown': '#f4a460',
+    'seagreen': '#2e8b57',
+    'seashell': '#fff5ee',
+    'sienna': '#a0522d',
+    'silver': '#c0c0c0',
+    'skyblue': '#87ceeb',
+    'slateblue': '#6a5acd',
+    'slategray': '#708090',
+    'slategrey': '#708090',
+    'snow': '#fffafa',
+    'springgreen': '#00ff7f',
+    'steelblue': '#4682b4',
+    'tan': '#d2b48c',
+    'teal': '#008080',
+    'thistle': '#d8bfd8',
+    'tomato': '#ff6347',
+    'turquoise': '#40e0d0',
+    'violet': '#ee82ee',
+    'wheat': '#f5deb3',
+    'white': '#ffffff',
+    'whitesmoke': '#f5f5f5',
+    'yellow': '#ffff00',
+    'yellowgreen': '#9acd32',
+}
+
 
 def parse_color(value: str):
     normalized = value.strip().lower()
 
-    if normalized == 'transparent':
+    if normalized in ('transparent', 'none'):
         return 0, 0, 0, 0
 
+    named_color = COLOR_NAME_HEX.get(normalized)
+
+    if named_color is not None:
+        normalized = named_color
+
     if normalized.startswith('#'):
         hex_value = normalized[1:]
 
@@ -408,12 +564,21 @@ def normalize_theme_file(data: dict):
         if isinstance(value, dict):
             dark = value.get('dark')
             light = value.get('light')
+
+            if dark is None and light is None:
+                raise SystemExit(f'theme token {token} must contain a color string or dark/light color strings')
+
+            if dark is None:
+                dark = light
+
+            if light is None:
+                light = dark
         else:
             dark = value
             light = value
 
         if not isinstance(dark, str) or not isinstance(light, str):
-            raise SystemExit(f'theme token {token} must contain color strings for dark and light')
+            raise SystemExit(f'theme token {token} must contain color strings')
 
         dark_rgba = parse_color(dark)
         light_rgba = parse_color(light)
diff --git a/src/app/themeEditorPageHelpers.test.ts b/src/app/themeEditorPageHelpers.test.ts
new file mode 100644
index 0000000..6402760
--- /dev/null
+++ b/src/app/themeEditorPageHelpers.test.ts
@@ -0,0 +1,51 @@
+import { describe, expect, it, vi } from 'vitest'
+import { createDefaultThemeDraft } from '../domain/theme/createDefaultThemeDraft'
+import { THEME_TOKEN_NAMES } from '../domain/theme/model'
+import { selectExportThemeFile } from '../state/selectors'
+import { applyJsonModeThemes } from './themeEditorPageHelpers'
+
+describe('applyJsonModeThemes', () => {
+  it('merges partial mode updates into the current resolved theme', () => {
+    const draft = createDefaultThemeDraft()
+    const replaceModeDraft = vi.fn()
+    const currentDarkTheme = selectExportThemeFile(draft, 'dark').theme
+
+    applyJsonModeThemes(
+      draft,
+      [...THEME_TOKEN_NAMES],
+      {
+        dark: {
+          text: '#008080',
+        },
+      },
+      replaceModeDraft,
+    )
+
+    expect(replaceModeDraft).toHaveBeenCalledTimes(1)
+    expect(replaceModeDraft).toHaveBeenCalledWith('dark', {
+      ...draft.modes.dark,
+      tokenOverrides: {
+        ...currentDarkTheme,
+        text: '#008080',
+      },
+    })
+  })
+
+  it('skips replacements when a partial update does not change the resolved theme', () => {
+    const draft = createDefaultThemeDraft()
+    const replaceModeDraft = vi.fn()
+
+    applyJsonModeThemes(
+      draft,
+      [...THEME_TOKEN_NAMES],
+      {
+        dark: {
+          text: selectExportThemeFile(draft, 'dark').theme.text,
+        },
+      },
+      replaceModeDraft,
+    )
+
+    expect(replaceModeDraft).not.toHaveBeenCalled()
+  })
+})
diff --git a/src/app/themeEditorPageHelpers.ts b/src/app/themeEditorPageHelpers.ts
index fffe074..7d13965 100644
--- a/src/app/themeEditorPageHelpers.ts
+++ b/src/app/themeEditorPageHelpers.ts
@@ -52,7 +52,11 @@ export function applyJsonModeThemes(
     }
 
     const currentThemeFile = selectExportThemeFile(draft, mode)
-    const hasChanges = tokenNames.some((token) => currentThemeFile.theme[token] !== modeTheme[token])
+    const nextTheme = {
+      ...currentThemeFile.theme,
+      ...modeTheme,
+    } satisfies ThemeTokens
+    const hasChanges = tokenNames.some((token) => currentThemeFile.theme[token] !== nextTheme[token])
 
     if (!hasChanges) {
       continue
@@ -60,7 +64,7 @@ export function applyJsonModeThemes(
 
     replaceModeDraft(mode, {
       ...draft.modes[mode],
-      tokenOverrides: modeTheme,
+      tokenOverrides: nextTheme,
     })
   }
 }
diff --git a/src/domain/theme/color.test.ts b/src/domain/theme/color.test.ts
index 6301e30..bf6e4d0 100644
--- a/src/domain/theme/color.test.ts
+++ b/src/domain/theme/color.test.ts
@@ -24,10 +24,13 @@ describe('color helpers', () => {
     expect(normalizeColorValue(' #AbC ')).toBe('#aabbcc')
     expect(normalizeColorValue('#abcd')).toBe('#aabbccdd')
     expect(normalizeColorValue('#ABCDEF')).toBe('#abcdef')
+    expect(normalizeColorValue('Teal')).toBe('#008080')
+    expect(normalizeColorValue('rebeccapurple')).toBe('#663399')
     expect(normalizeColorValue('none')).toBe('transparent')
     expect(normalizeColorValue('transparent')).toBe('transparent')
     expect(normalizeColorValue('rgb(1, 2, 3)')).toBeNull()
     expect(isColorValue('#123456')).toBe(true)
+    expect(isColorValue('teal')).toBe(true)
     expect(isColorValue('oops')).toBe(false)
   })
 
@@ -50,6 +53,12 @@ describe('color helpers', () => {
       b: 0,
       a: 0,
     })
+    expect(parseColor('teal')).toEqual({
+      r: 0,
+      g: 128,
+      b: 128,
+      a: 1,
+    })
     expect(parseColor('invalid')).toBeNull()
 
     expect(
@@ -95,6 +104,7 @@ describe('color helpers', () => {
   it('normalizes equality and color input helpers', () => {
     expect(areColorValuesEqual('#abc', '#aabbcc')).toBe(true)
     expect(areColorValuesEqual('transparent', 'none')).toBe(true)
+    expect(areColorValuesEqual('teal', '#008080')).toBe(true)
     expect(areColorValuesEqual('#abc', '#000000')).toBe(false)
 
     expect(getColorInputValue('#12345680')).toBe('#123456')
diff --git a/src/domain/theme/colorCore.ts b/src/domain/theme/colorCore.ts
index 53b4fa3..2ea9ac2 100644
--- a/src/domain/theme/colorCore.ts
+++ b/src/domain/theme/colorCore.ts
@@ -1,3 +1,5 @@
+import { CSS_NAMED_COLORS } from './namedColors'
+
 export type ParsedColor = {
   r: number
   g: number
@@ -29,17 +31,24 @@ export function clampAlpha(value: number) {
 
 export function normalizeColorValue(value: string) {
   const trimmed = value.trim()
+  const lowered = trimmed.toLowerCase()
 
-  if (TRANSPARENT_COLOR_PATTERN.test(trimmed)) {
+  if (TRANSPARENT_COLOR_PATTERN.test(lowered)) {
     return 'transparent'
   }
 
-  if (HEX_3_COLOR_PATTERN.test(trimmed) || HEX_4_COLOR_PATTERN.test(trimmed)) {
-    return expandShortHex(trimmed.toLowerCase())
+  if (HEX_3_COLOR_PATTERN.test(lowered) || HEX_4_COLOR_PATTERN.test(lowered)) {
+    return expandShortHex(lowered)
+  }
+
+  if (HEX_6_COLOR_PATTERN.test(lowered) || HEX_8_COLOR_PATTERN.test(lowered)) {
+    return lowered
   }
 
-  if (HEX_6_COLOR_PATTERN.test(trimmed) || HEX_8_COLOR_PATTERN.test(trimmed)) {
-    return trimmed.toLowerCase()
+  const namedColor = CSS_NAMED_COLORS[lowered as keyof typeof CSS_NAMED_COLORS]
+
+  if (namedColor !== undefined) {
+    return namedColor
   }
 
   return null
diff --git a/src/domain/theme/namedColors.ts b/src/domain/theme/namedColors.ts
new file mode 100644
index 0000000..27167e7
--- /dev/null
+++ b/src/domain/theme/namedColors.ts
@@ -0,0 +1,150 @@
+export const CSS_NAMED_COLORS = {
+  aliceblue: '#f0f8ff',
+  antiquewhite: '#faebd7',
+  aqua: '#00ffff',
+  aquamarine: '#7fffd4',
+  azure: '#f0ffff',
+  beige: '#f5f5dc',
+  bisque: '#ffe4c4',
+  black: '#000000',
+  blanchedalmond: '#ffebcd',
+  blue: '#0000ff',
+  blueviolet: '#8a2be2',
+  brown: '#a52a2a',
+  burlywood: '#deb887',
+  cadetblue: '#5f9ea0',
+  chartreuse: '#7fff00',
+  chocolate: '#d2691e',
+  coral: '#ff7f50',
+  cornflowerblue: '#6495ed',
+  cornsilk: '#fff8dc',
+  crimson: '#dc143c',
+  cyan: '#00ffff',
+  darkblue: '#00008b',
+  darkcyan: '#008b8b',
+  darkgoldenrod: '#b8860b',
+  darkgray: '#a9a9a9',
+  darkgreen: '#006400',
+  darkgrey: '#a9a9a9',
+  darkkhaki: '#bdb76b',
+  darkmagenta: '#8b008b',
+  darkolivegreen: '#556b2f',
+  darkorange: '#ff8c00',
+  darkorchid: '#9932cc',
+  darkred: '#8b0000',
+  darksalmon: '#e9967a',
+  darkseagreen: '#8fbc8f',
+  darkslateblue: '#483d8b',
+  darkslategray: '#2f4f4f',
+  darkslategrey: '#2f4f4f',
+  darkturquoise: '#00ced1',
+  darkviolet: '#9400d3',
+  deeppink: '#ff1493',
+  deepskyblue: '#00bfff',
+  dimgray: '#696969',
+  dimgrey: '#696969',
+  dodgerblue: '#1e90ff',
+  firebrick: '#b22222',
+  floralwhite: '#fffaf0',
+  forestgreen: '#228b22',
+  fuchsia: '#ff00ff',
+  gainsboro: '#dcdcdc',
+  ghostwhite: '#f8f8ff',
+  gold: '#ffd700',
+  goldenrod: '#daa520',
+  gray: '#808080',
+  green: '#008000',
+  greenyellow: '#adff2f',
+  grey: '#808080',
+  honeydew: '#f0fff0',
+  hotpink: '#ff69b4',
+  indianred: '#cd5c5c',
+  indigo: '#4b0082',
+  ivory: '#fffff0',
+  khaki: '#f0e68c',
+  lavender: '#e6e6fa',
+  lavenderblush: '#fff0f5',
+  lawngreen: '#7cfc00',
+  lemonchiffon: '#fffacd',
+  lightblue: '#add8e6',
+  lightcoral: '#f08080',
+  lightcyan: '#e0ffff',
+  lightgoldenrodyellow: '#fafad2',
+  lightgray: '#d3d3d3',
+  lightgreen: '#90ee90',
+  lightgrey: '#d3d3d3',
+  lightpink: '#ffb6c1',
+  lightsalmon: '#ffa07a',
+  lightseagreen: '#20b2aa',
+  lightskyblue: '#87cefa',
+  lightslategray: '#778899',
+  lightslategrey: '#778899',
+  lightsteelblue: '#b0c4de',
+  lightyellow: '#ffffe0',
+  lime: '#00ff00',
+  limegreen: '#32cd32',
+  linen: '#faf0e6',
+  magenta: '#ff00ff',
+  maroon: '#800000',
+  mediumaquamarine: '#66cdaa',
+  mediumblue: '#0000cd',
+  mediumorchid: '#ba55d3',
+  mediumpurple: '#9370db',
+  mediumseagreen: '#3cb371',
+  mediumslateblue: '#7b68ee',
+  mediumspringgreen: '#00fa9a',
+  mediumturquoise: '#48d1cc',
+  mediumvioletred: '#c71585',
+  midnightblue: '#191970',
+  mintcream: '#f5fffa',
+  mistyrose: '#ffe4e1',
+  moccasin: '#ffe4b5',
+  navajowhite: '#ffdead',
+  navy: '#000080',
+  oldlace: '#fdf5e6',
+  olive: '#808000',
+  olivedrab: '#6b8e23',
+  orange: '#ffa500',
+  orangered: '#ff4500',
+  orchid: '#da70d6',
+  palegoldenrod: '#eee8aa',
+  palegreen: '#98fb98',
+  paleturquoise: '#afeeee',
+  palevioletred: '#db7093',
+  papayawhip: '#ffefd5',
+  peachpuff: '#ffdab9',
+  peru: '#cd853f',
+  pink: '#ffc0cb',
+  plum: '#dda0dd',
+  powderblue: '#b0e0e6',
+  purple: '#800080',
+  rebeccapurple: '#663399',
+  red: '#ff0000',
+  rosybrown: '#bc8f8f',
+  royalblue: '#4169e1',
+  saddlebrown: '#8b4513',
+  salmon: '#fa8072',
+  sandybrown: '#f4a460',
+  seagreen: '#2e8b57',
+  seashell: '#fff5ee',
+  sienna: '#a0522d',
+  silver: '#c0c0c0',
+  skyblue: '#87ceeb',
+  slateblue: '#6a5acd',
+  slategray: '#708090',
+  slategrey: '#708090',
+  snow: '#fffafa',
+  springgreen: '#00ff7f',
+  steelblue: '#4682b4',
+  tan: '#d2b48c',
+  teal: '#008080',
+  thistle: '#d8bfd8',
+  tomato: '#ff6347',
+  turquoise: '#40e0d0',
+  violet: '#ee82ee',
+  wheat: '#f5deb3',
+  white: '#ffffff',
+  whitesmoke: '#f5f5f5',
+  yellow: '#ffff00',
+  yellowgreen: '#9acd32',
+} as const
diff --git a/src/features/editor/JsonThemeEditor.test.tsx b/src/features/editor/JsonThemeEditor.test.tsx
index e095035..c087734 100644
--- a/src/features/editor/JsonThemeEditor.test.tsx
+++ b/src/features/editor/JsonThemeEditor.test.tsx
@@ -66,7 +66,7 @@ describe('JsonThemeEditor', () => {
           {
             $schema: 'https://opencode.ai/theme.json',
             defs: {
-              'dark-text': '#111111',
+              'dark-text': 'teal',
               'light-text': '#EEE',
             },
             theme: exportCombinedThemeFile(darkTheme as typeof props.themeFile.theme, lightTheme as typeof props.themeFile.theme).theme,
@@ -81,7 +81,7 @@ describe('JsonThemeEditor', () => {
 
     expect(payload.dark).toEqual(
       expect.objectContaining({
-        text: '#111111',
+        text: '#008080',
       }),
     )
     expect(payload.light).toEqual(
@@ -91,6 +91,70 @@ describe('JsonThemeEditor', () => {
     )
   })
 
+  it('applies a dark-only combined edit and leaves light mode unchanged', () => {
+    const props = buildProps('dark')
+    const darkOnlyTheme = Object.fromEntries(
+      props.tokenNames.map((token) => [token, { dark: token === 'text' ? 'teal' : props.combinedThemeFile.theme[token].dark }]),
+    )
+
+    render(<JsonThemeEditor {...props} />)
+
+    fireEvent.change(screen.getByLabelText('Theme JSON editor'), {
+      target: {
+        value: JSON.stringify(
+          {
+            $schema: 'https://opencode.ai/theme.json',
+            theme: darkOnlyTheme,
+          },
+          null,
+          2,
+        ),
+      },
+    })
+
+    const payload = props.onChange.mock.lastCall?.[0]
+
+    expect(payload.dark).toEqual(
+      expect.objectContaining({
+        text: '#008080',
+      }),
+    )
+    expect(payload.light).toBeUndefined()
+    expect(screen.queryByRole('status')).not.toBeInTheDocument()
+  })
+
+  it('applies a light-only combined edit and leaves dark mode unchanged', () => {
+    const props = buildProps('dark')
+    const lightOnlyTheme = Object.fromEntries(
+      props.tokenNames.map((token) => [token, { light: token === 'text' ? 'teal' : props.combinedThemeFile.theme[token].light }]),
+    )
+
+    render(<JsonThemeEditor {...props} />)
+
+    fireEvent.change(screen.getByLabelText('Theme JSON editor'), {
+      target: {
+        value: JSON.stringify(
+          {
+            $schema: 'https://opencode.ai/theme.json',
+            theme: lightOnlyTheme,
+          },
+          null,
+          2,
+        ),
+      },
+    })
+
+    const payload = props.onChange.mock.lastCall?.[0]
+
+    expect(payload.dark).toBeUndefined()
+    expect(payload.light).toEqual(
+      expect.objectContaining({
+        text: '#008080',
+      }),
+    )
+    expect(screen.queryByRole('status')).not.toBeInTheDocument()
+  })
+
   it('shows the current mixed-format validation error', () => {
     const props = buildProps('dark')
 
@@ -182,11 +246,17 @@ describe('JsonThemeEditor', () => {
             props.onChange(modeThemes)
 
             if (modeThemes.dark) {
-              setDarkTheme(modeThemes.dark)
+              setDarkTheme((current) => ({
+                ...current,
+                ...modeThemes.dark,
+              }))
             }
 
             if (modeThemes.light) {
-              setLightTheme(modeThemes.light)
+              setLightTheme((current) => ({
+                ...current,
+                ...modeThemes.light,
+              }))
             }
           }}
         />
diff --git a/src/features/editor/jsonThemeEditorParser.ts b/src/features/editor/jsonThemeEditorParser.ts
index 56bbb90..6fb5131 100644
--- a/src/features/editor/jsonThemeEditorParser.ts
+++ b/src/features/editor/jsonThemeEditorParser.ts
@@ -7,7 +7,7 @@ import {
 import { normalizeColorValue } from '../../domain/theme/color'
 import type { ThemeMode, ThemeTokenName, ThemeTokens } from '../../domain/theme/model'
 
-export type JsonThemeModeUpdates = Partial<Record<ThemeMode, ThemeTokens>>
+export type JsonThemeModeUpdates = Partial<Record<ThemeMode, Partial<ThemeTokens>>>
 
 export type ParseJsonThemeResult =
   | {
@@ -127,31 +127,92 @@ function parseCombinedTheme(
 ): ParseJsonThemeResult {
   const darkTheme = {} as ThemeTokens
   const lightTheme = {} as ThemeTokens
+  const darkModeUpdates: Partial<ThemeTokens> = {}
+  const lightModeUpdates: Partial<ThemeTokens> = {}
+  let hasDarkValues = false
+  let hasLightValues = false
 
   for (const token of tokenNames) {
     const tokenValue = theme[token]
 
-    if (!isRecord(tokenValue) || typeof tokenValue.dark !== 'string' || typeof tokenValue.light !== 'string') {
+    if (!isRecord(tokenValue)) {
       return {
         ok: false,
-        error: `Token \`${token}\` must include string \`dark\` and \`light\` values`,
+        error: `Token \`${token}\` must be an object with string \`dark\` and/or \`light\` values`,
       }
     }
 
-    const resolvedDark = resolveThemeTokenColor(tokenValue.dark, defs, token)
+    const rawDark = tokenValue.dark
+    const rawLight = tokenValue.light
 
-    if (!resolvedDark.ok) {
+    if (rawDark !== undefined && typeof rawDark !== 'string') {
+      return {
+        ok: false,
+        error: `Token \`${token}\` \`dark\` value must be a string when provided`,
+      }
+    }
+
+    if (rawLight !== undefined && typeof rawLight !== 'string') {
+      return {
+        ok: false,
+        error: `Token \`${token}\` \`light\` value must be a string when provided`,
+      }
+    }
+
+    if (rawDark === undefined && rawLight === undefined) {
+      return {
+        ok: false,
+        error: `Token \`${token}\` must include a string \`dark\` or \`light\` value`,
+      }
+    }
+
+    const resolvedDark =
+      rawDark === undefined
+        ? null
+        : resolveThemeTokenColor(rawDark, defs, token)
+
+    if (resolvedDark && !resolvedDark.ok) {
       return { ok: false, error: resolvedDark.error }
     }
 
-    const resolvedLight = resolveThemeTokenColor(tokenValue.light, defs, token)
+    const resolvedLight =
+      rawLight === undefined
+        ? null
+        : resolveThemeTokenColor(rawLight, defs, token)
 
-    if (!resolvedLight.ok) {
+    if (resolvedLight && !resolvedLight.ok) {
       return { ok: false, error: resolvedLight.error }
     }
 
-    darkTheme[token] = resolvedDark.value
-    lightTheme[token] = resolvedLight.value
+    if (resolvedDark) {
+      darkModeUpdates[token] = resolvedDark.value
+      darkTheme[token] = resolvedDark.value
+      hasDarkValues = true
+    }
+
+    if (resolvedLight) {
+      lightModeUpdates[token] = resolvedLight.value
+      lightTheme[token] = resolvedLight.value
+      hasLightValues = true
+    }
+
+    if (!resolvedDark && resolvedLight) {
+      darkTheme[token] = resolvedLight.value
+    }
+
+    if (!resolvedLight && resolvedDark) {
+      lightTheme[token] = resolvedDark.value
+    }
+  }
+
+  const modeThemes: JsonThemeModeUpdates = {}
+
+  if (hasDarkValues) {
+    modeThemes.dark = darkModeUpdates
+  }
+
+  if (hasLightValues) {
+    modeThemes.light = lightModeUpdates
   }
 
   return {
@@ -159,10 +220,7 @@ function parseCombinedTheme(
     value: {
       format: 'combined',
       themeFile: exportCombinedThemeFile(darkTheme, lightTheme),
-      modeThemes: {
-        dark: darkTheme,
-        light: lightTheme,
-      },
+      modeThemes,
     },
   }
 }
@@ -244,7 +302,7 @@ export function parseJsonThemeFile(value: string, tokenNames: ThemeTokenName[],
 
     return {
       ok: false,
-      error: `Token \`${token}\` must be a string or an object with \`dark\` and \`light\``,
+      error: `Token \`${token}\` must be a string or an object with \`dark\` and/or \`light\``,
     }
   }