Dark Mode Generation Skill

Overview

Automatically generate dark mode color schemes from light mode designs with intelligent color inversion, contrast preservation, and accessibility compliance (WCAG 2.2).

Input: Light mode component Output: Dark mode CSS variables, color mappings, theme toggle, updated stories

How It Works

1. Analyze Light Mode Colors

Extract all colors from component:

// Detected colors
Background: #FFFFFF
Text: #1F2937 (gray-800)
Primary: #2196F3 (blue-500)
Border: #E5E7EB (gray-200)
Shadow: rgba(0, 0, 0, 0.1)

2. Generate Dark Palette

Apply intelligent transformations:

/* Light Mode */
--bg-primary: #FFFFFF;      /* white */
--text-primary: #1F2937;    /* dark gray */
--color-primary: #2196F3;   /* blue */
--border: #E5E7EB;          /* light gray */

/* Dark Mode (Generated) */
--bg-primary: #1F2937;      /* dark gray (inverted) */
--text-primary: #F9FAFB;    /* off-white (inverted) */
--color-primary: #60A5FA;   /* lighter blue (adjusted for contrast) */
--border: #374151;          /* medium gray (adjusted) */

Rules:

• Backgrounds: Darken significantly (#FFF → #1F2937)
• Text: Lighten for readability (#000 → #F9FAFB)
• Brand colors: Adjust for contrast (may lighten or darken)
• Borders: Medium grays (#E5E7EB → #374151)
• Shadows: Invert or remove (dark shadows on dark BG don't work)

3. Preserve Contrast Ratios

Ensure WCAG compliance maintained:

Light Mode: #1F2937 on #FFFFFF = 16.1:1 (AAA) ✓
Dark Mode:  #F9FAFB on #1F2937 = 15.8:1 (AAA) ✓

Light Mode: #2196F3 on #FFFFFF = 3.1:1 (AA Large) ✓
Dark Mode:  #60A5FA on #1F2937 = 4.7:1 (AA Normal) ✓ (Improved!)

4. Generate Theme System

Create complete dark mode implementation:

CSS Variables:

/* themes/colors.css */
:root {
  --bg-primary: #FFFFFF;
  --bg-secondary: #F9FAFB;
  --text-primary: #1F2937;
  --text-secondary: #6B7280;
  --color-primary: #2196F3;
  --border: #E5E7EB;
  --shadow: rgba(0, 0, 0, 0.1);
}

[data-theme="dark"] {
  --bg-primary: #1F2937;
  --bg-secondary: #111827;
  --text-primary: #F9FAFB;
  --text-secondary: #D1D5DB;
  --color-primary: #60A5FA;
  --border: #374151;
  --shadow: rgba(0, 0, 0, 0.3);
}

Theme Toggle Component:

// components/ThemeToggle.tsx
'use client';

import { useEffect, useState } from 'react';
import { Moon, Sun } from 'lucide-react';

export function ThemeToggle() {
  const [theme, setTheme] = useState<'light' | 'dark'>('light');

  useEffect(() => {
    const saved = localStorage.getItem('theme') || 'light';
    setTheme(saved as 'light' | 'dark');
    document.documentElement.setAttribute('data-theme', saved);
  }, []);

  const toggleTheme = () => {
    const newTheme = theme === 'light' ? 'dark' : 'light';
    setTheme(newTheme);
    document.documentElement.setAttribute('data-theme', newTheme);
    localStorage.setItem('theme', newTheme);
  };

  return (
    <button
      onClick={toggleTheme}
      aria-label={`Switch to ${theme === 'light' ? 'dark' : 'light'} mode`}
      className="p-2 rounded-lg hover:bg-gray-100 dark:hover:bg-gray-800"
    >
      {theme === 'light' ? <Moon size={20} /> : <Sun size={20} />}
    </button>
  );
}

5. Update Storybook Stories

Add dark mode variants:

// Button.stories.tsx
export const LightMode: Story = {
  parameters: {
    backgrounds: { default: 'light' },
    theme: 'light',
  },
};

export const DarkMode: Story = {
  parameters: {
    backgrounds: { default: 'dark' },
    theme: 'dark',
  },
  decorators: [
    (Story) => (
      <div data-theme="dark">
        <Story />
      </div>
    ),
  ],
};

export const AllThemes: Story = {
  render: () => (
    <div className="grid grid-cols-2 gap-4">
      <div data-theme="light" className="p-4 bg-white">
        <h3>Light Mode</h3>
        <Button variant="primary">Click me</Button>
      </div>
      <div data-theme="dark" className="p-4 bg-gray-900">
        <h3>Dark Mode</h3>
        <Button variant="primary">Click me</Button>
      </div>
    </div>
  ),
};

Color Transformation Rules

Surface Colors

Light → Dark
#FFFFFF → #1F2937  (primary background)
#F9FAFB → #111827  (secondary background)
#F3F4F6 → #0F172A  (tertiary background)

Text Colors

Light → Dark
#111827 → #F9FAFB  (primary text)
#374151 → #E5E7EB  (secondary text)
#6B7280 → #9CA3AF  (tertiary text)

Brand Colors

Adjust for contrast, not just invert:

Primary Blue:
#2196F3 → #60A5FA  (lighter for dark BG)

Success Green:
#10B981 → #34D399  (lighter)

Error Red:
#EF4444 → #F87171  (lighter)

Warning Yellow:
#F59E0B → #FBBF24  (lighter)

Borders & Dividers

#E5E7EB → #374151  (visible on dark)
#D1D5DB → #4B5563  (medium)
#9CA3AF → #6B7280  (subtle)

Shadows

Light Mode: rgba(0, 0, 0, 0.1)
Dark Mode: rgba(0, 0, 0, 0.3)  (darker, more pronounced)

Semantic Color Mapping

Maintain semantic meaning across themes:

/* Semantic tokens */
:root {
  --color-success: #10B981;
  --color-warning: #F59E0B;
  --color-error: #EF4444;
  --color-info: #3B82F6;
}

[data-theme="dark"] {
  --color-success: #34D399;  /* Lighter green */
  --color-warning: #FBBF24;  /* Lighter yellow */
  --color-error: #F87171;    /* Lighter red */
  --color-info: #60A5FA;     /* Lighter blue */
}

Best Practices

✅ Do's

• Test contrast ratios (use WCAG checker)
• Adjust brand colors for readability
• Provide theme toggle in accessible location
• Persist user preference (localStorage)
• Use CSS variables for easy switching
• Test with real users in dark environments

❌ Don'ts

• Don't just invert all colors
• Don't use pure black (#000) as background (harsh)
• Don't forget to adjust shadows
• Don't ignore semantic colors (success, error, etc.)
• Don't make dark mode an afterthought

Integration

With Tailwind CSS

// tailwind.config.js
module.exports = {
  darkMode: 'class',  // or 'media'
  theme: {
    extend: {
      colors: {
        primary: {
          light: '#2196F3',
          dark: '#60A5FA',
        },
      },
    },
  },
};

// Usage
<div className="bg-white dark:bg-gray-900">
  <h1 className="text-gray-900 dark:text-gray-100">

With CSS Modules

/* Component.module.css */
.container {
  background: var(--bg-primary);
  color: var(--text-primary);
}

[data-theme="dark"] .container {
  /* Inherits CSS variables */
}

Files Generated

1. themes/colors.css - CSS variable definitions
2. components/ThemeToggle.tsx - Theme switcher
3. stories/ThemePreviews.stories.tsx - Side-by-side comparisons
4. docs/DarkModeGuide.md - Usage documentation

Summary

Automatic dark mode generation:

1. Analyzes light mode colors
2. Generates accessible dark palette
3. Creates theme system (CSS vars + toggle)
4. Updates Storybook stories
5. Maintains WCAG compliance

Result: Production-ready dark mode in minutes, not hours.