Colour Palette Generator

Generate a complete, accessible colour system from a single brand hex. Produces Tailwind v4 CSS ready to paste into your project.

Workflow

Step 1: Get the Brand Hex

Ask for the primary brand colour. A single hex like #0D9488 is enough.

Step 2: Generate 11-Shade Scale

Convert hex to HSL, then generate shades by varying lightness while keeping hue constant.

Hex to HSL Conversion

function hexToHSL(hex) {
  hex = hex.replace(/^#/, '');
  const r = parseInt(hex.substring(0, 2), 16) / 255;
  const g = parseInt(hex.substring(2, 4), 16) / 255;
  const b = parseInt(hex.substring(4, 6), 16) / 255;

  const max = Math.max(r, g, b);
  const min = Math.min(r, g, b);
  const diff = max - min;

  let l = (max + min) / 2;
  let s = 0;
  if (diff !== 0) {
    s = l > 0.5 ? diff / (2 - max - min) : diff / (max + min);
  }

  let h = 0;
  if (diff !== 0) {
    if (max === r) h = ((g - b) / diff + (g < b ? 6 : 0)) / 6;
    else if (max === g) h = ((b - r) / diff + 2) / 6;
    else h = ((r - g) / diff + 4) / 6;
  }

  return { h: Math.round(h * 360), s: Math.round(s * 100), l: Math.round(l * 100) };
}

Lightness and Saturation Values

Reduce saturation for lighter shades (50-200 by 15-20%, 300-400 by 5-10%) to prevent overly vibrant pastels. Keep full saturation for 500-950.

Complete Scale Generator

function generateShadeScale(brandHex) {
  const { h, s } = hexToHSL(brandHex);
  const shades = {
    50:  { l: 97, sMul: 0.8 },  100: { l: 94, sMul: 0.8 },
    200: { l: 87, sMul: 0.85 }, 300: { l: 75, sMul: 0.9 },
    400: { l: 62, sMul: 0.95 }, 500: { l: 48, sMul: 1.0 },
    600: { l: 40, sMul: 1.0 },  700: { l: 33, sMul: 1.0 },
    800: { l: 27, sMul: 1.0 },  900: { l: 20, sMul: 1.0 },
    950: { l: 10, sMul: 1.0 }
  };
  const result = {};
  for (const [shade, { l, sMul }] of Object.entries(shades)) {
    result[shade] = `hsl(${h}, ${Math.round(s * sMul)}%, ${l}%)`;
  }
  return result;
}

HSL to Hex Conversion

function hslToHex(h, s, l) {
  s = s / 100; l = l / 100;
  const c = (1 - Math.abs(2 * l - 1)) * s;
  const x = c * (1 - Math.abs((h / 60) % 2 - 1));
  const m = l - c / 2;
  let r = 0, g = 0, b = 0;
  if (h < 60) { r = c; g = x; }
  else if (h < 120) { r = x; g = c; }
  else if (h < 180) { g = c; b = x; }
  else if (h < 240) { g = x; b = c; }
  else if (h < 300) { r = x; b = c; }
  else { r = c; b = x; }
  r = Math.round((r + m) * 255);
  g = Math.round((g + m) * 255);
  b = Math.round((b + m) * 255);
  return `#${r.toString(16).padStart(2, '0')}${g.toString(16).padStart(2, '0')}${b.toString(16).padStart(2, '0')}`.toUpperCase();
}

Verification

Generated shades should look like the same colour family with smooth progression. Light shades (50-300) usable for backgrounds, dark shades (700-950) usable for text. Brand colour recognisable in 500-700.

Step 3: Map Semantic Tokens

Every background token MUST have a paired foreground token. Never use a background without its pair or dark mode will break.

Light Mode Tokens

Dark Mode Tokens

Dark Mode Inversion Pattern

Dark mode inverts lightness while preserving hue and saturation. Swap extremes (50 becomes 950, 950 becomes 50), preserve middle (500 stays near 500).

Key dark mode principles:

• Use shade 500 (not 600) for primary -- brighter for visibility on dark backgrounds
• Use shade 50 (off-white) for text instead of pure #FFFFFF -- easier on eyes
• Borders need ~10-15% lighter than background (e.g. 800 border on 950 background)
• Higher elevation = lighter colour (opposite of light mode shadows)
• Always update foreground when changing background

Step 4: Check Contrast

WCAG Minimum Ratios

Target AA for most projects, AAA for high-accessibility needs (government, healthcare).

Luminance and Contrast Formulas

function getLuminance(hex) {
  hex = hex.replace(/^#/, '');
  const r = parseInt(hex.substring(0, 2), 16) / 255;
  const g = parseInt(hex.substring(2, 4), 16) / 255;
  const b = parseInt(hex.substring(4, 6), 16) / 255;
  const rsRGB = r <= 0.03928 ? r / 12.92 : Math.pow((r + 0.055) / 1.055, 2.4);
  const gsRGB = g <= 0.03928 ? g / 12.92 : Math.pow((g + 0.055) / 1.055, 2.4);
  const bsRGB = b <= 0.03928 ? b / 12.92 : Math.pow((b + 0.055) / 1.055, 2.4);
  return 0.2126 * rsRGB + 0.7152 * gsRGB + 0.0722 * bsRGB;
}

function getContrastRatio(hex1, hex2) {
  const lum1 = getLuminance(hex1);
  const lum2 = getLuminance(hex2);
  const lighter = Math.max(lum1, lum2);
  const darker = Math.min(lum1, lum2);
  return (lighter + 0.05) / (darker + 0.05);
}

Quick Check Table -- Light Mode