Color Contrast Auditor

Detects color contrast violations that make text unreadable and provides WCAG-compliant fixes. Uses both mathematical contrast ratio analysis and perceptual evaluation via vision capabilities.

When to Use

Activate on:

Screenshots of websites/apps with suspected contrast issues CSS/Tailwind files for color audit "I can't read this" or "this is hard to see" Pre-launch accessibility checks Design system color validation

NOT for:

Choosing brand colors (use web-design-expert) Color harmony/aesthetics (use color-theory-palette-harmony-expert) Non-visual accessibility (screen readers, keyboard nav) WCAG 2.1 Contrast Requirements Minimum Ratios (AA - Required) Text Type Minimum Ratio Example Normal text (<24px, <18.66px bold) 4.5:1 Body copy, labels, buttons Large text (≥24px or ≥18.66px bold) 3:1 Headlines, hero text UI components (borders, icons) 3:1 Form inputs, icons, focus rings Graphical objects 3:1 Charts, infographics Enhanced Ratios (AAA - Recommended) Text Type Minimum Ratio Normal text 7:1 Large text 4.5:1 Non-Text Elements Element Requirement Focus indicators 3:1 against adjacent colors Form field borders 3:1 against background Icons conveying meaning 3:1 against background Disabled elements No requirement (but consider UX) Contrast Ratio Formula Contrast Ratio = (L1 + 0.05) / (L2 + 0.05)

Where L1 = lighter color's relative luminance L2 = darker color's relative luminance

Calculating Relative Luminance function relativeLuminance(r, g, b) { // Convert 0-255 to 0-1 let [rs, gs, bs] = [r, g, b].map(c => c / 255);

// Apply gamma correction const gamma = c => c <= 0.03928 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4);

const [R, G, B] = [rs, gs, bs].map(gamma);

// Weighted sum (human eye sensitivity) return 0.2126 * R + 0.7152 * G + 0.0722 * B; }

function contrastRatio(color1, color2) { const l1 = relativeLuminance(...color1); const l2 = relativeLuminance(...color2); const lighter = Math.max(l1, l2); const darker = Math.min(l1, l2); return (lighter + 0.05) / (darker + 0.05); }

Common Failing Patterns 1. Light Text on Light Background ❌ FAILING EXAMPLE (from user screenshot):

┌─────────────────────────────────────────────┐ │ Background: #F5F2E8 (beige/cream) │ │ Text: #C8FF00 (lime green) │ │ │ │ "Scan. Crawl. Match. Report." │ │ ← UNREADABLE │ │ │ │ Calculated Ratio: ~1.5:1 │ │ Required: 4.5:1 (normal) or 3:1 (large) │ │ Verdict: FAIL by 3x │ └─────────────────────────────────────────────┘

✅ FIXED OPTIONS: • Darken text to #5A7300 → Ratio: 4.5:1 • Darken background to #2A2A2A → Ratio: 12:1 • Use dark green #1A4D00 → Ratio: 8:1

Gray Text Syndrome ❌ COMMON FAILURE: Background: #FFFFFF Text: #AAAAAA (light gray) Ratio: 2.3:1 ← FAIL

✅ FIXES: • Text: #767676 → Ratio: 4.5:1 (minimum AA) • Text: #595959 → Ratio: 7:1 (AAA)

Saturated Colors That Look Bright ❌ DECEPTIVE FAILURE: Background: #FFF8E7 (warm white) Text: #FF6B6B (coral/salmon) Ratio: 2.8:1 ← FAIL (looks "colorful" but fails)

✅ FIXES: • Text: #C62828 (darker red) → Ratio: 5.2:1 • Text: #8B0000 (dark red) → Ratio: 8.1:1

Trendy Low-Contrast Aesthetic ❌ "MINIMALIST" FAILURE: Background: #FAFAFA Text: #E0E0E0 Ratio: 1.3:1 ← SEVERELY FAILING

This is NOT minimalism. This is inaccessible.

✅ MINIMALIST + ACCESSIBLE: Background: #FAFAFA Text: #616161 → Ratio: 5.7:1

Placeholder Text Too Light ❌ COMMON FORM FAILURE: Input background: #FFFFFF Placeholder: #CCCCCC Ratio: 1.6:1 ← FAIL

✅ FIX: Placeholder: #757575 → Ratio: 4.6:1

Gradient Backgrounds ❌ VARIABLE CONTRAST: Gradient: #FFFFFF → #000080 Text: #FFFFFF (fixed)

Top of gradient: 1:1 (invisible!) Bottom of gradient: 8.6:1 (good)

✅ SOLUTIONS: • Add text shadow/outline • Use semi-transparent overlay behind text • Ensure ALL gradient stops pass contrast

Audit Methodology Step 1: Visual Scan (Screenshot Analysis)

When given a screenshot, identify:

Text elements by size:

Headlines (large text → 3:1 required) Body copy (normal text → 4.5:1 required) UI labels (buttons, links → 4.5:1) Captions/fine print (4.5:1 required)

Interactive elements:

Button borders/backgrounds Form field borders Focus states Icons with meaning

Red flags to look for:

Light text on light backgrounds Gray text on white Colored text on colored backgrounds Text over images without overlay Step 2: Extract Colors

From CSS/code:

Find all color declarations

grep -E "(color:|background:|#[0-9a-fA-F]{3,8}|rgb|hsl)" styles.css

From Tailwind:

Find text/bg color classes

grep -E "(text-|bg-)" .tsx .jsx

Step 3: Calculate Ratios

For each text/background pair:

Convert colors to RGB Calculate relative luminance Compute contrast ratio Compare to WCAG requirement Step 4: Generate Report

Contrast Audit Report

Summary

Total color pairs tested: X
Passing (AA): Y
Failing: Z
Critical failures (<2:1): N

Failures by Severity

Critical (Ratio < 2:1)

|----------|------------|------------|-------|----------|-----|

| Hero tagline | #C8FF00 | #F5F2E8 | 1.5:1 | 3:1 | #5A7300 |

Moderate (Ratio 2:1 - 3:1)

...

Minor (Ratio 3:1 - 4.5:1, normal text only)

...

Recommended Fixes

[Specific color replacements with new ratios]

Color Blindness Considerations

Contrast requirements help but don't fully address color blindness. Additional checks:

Types to Consider Type Affected Consideration Deuteranopia 6% of males Red/green confusion Protanopia 2% of males Red appears dark Tritanopia <1% Blue/yellow confusion Best Practices

Never rely on color alone for meaning

Add icons, patterns, or text labels Red/green for error/success needs icons too

Test problematic pairs:

Red + Green (stop/go) Blue + Purple Green + Brown Light green + Yellow

Use sufficient lightness difference

Even with same hue, different lightness helps Quick Reference: Safe Color Pairs On White (#FFFFFF) Use Case Color Hex Ratio Body text Dark gray #333333 12.6:1 Secondary text Medium gray #767676 4.5:1 Links Blue #0066CC 5.3:1 Success Green #2E7D32 5.1:1 Error Red #C62828 6.0:1 Warning Orange-brown #E65100 4.5:1 On Black (#000000) Use Case Color Hex Ratio Body text Light gray #E0E0E0 13.4:1 Secondary Medium gray #9E9E9E 6.3:1 Accent Light blue #90CAF9 7.3:1 On Dark Gray (#1A1A1A) Use Case Color Hex Ratio Body text Off-white #F5F5F5 14.1:1 Secondary Light gray #BDBDBD 8.3:1 Tools & Validation Online Checkers WebAIM Contrast Checker Coolors Contrast Checker Adobe Color Accessibility Browser DevTools // Chrome DevTools: Elements → Styles → hover color swatch // Shows contrast ratio automatically

// Firefox: Accessibility Inspector // Shows color contrast issues

Automated Testing // axe-core (popular a11y testing library) const axe = require('axe-core'); axe.run(document, { rules: ['color-contrast'] });

// Lighthouse (built into Chrome) // Performance → Accessibility → Color contrast

CLI Tools

Lighthouse CLI

npx lighthouse https://example.com --only-categories=accessibility

Pa11y

npx pa11y https://example.com

Integration with This Skill

When analyzing a screenshot or codebase:

I will identify all text/background color pairs I will calculate contrast ratios for each I will flag anything below WCAG AA thresholds I will suggest specific hex values that pass I will provide before/after comparisons

For the example screenshot (lime on beige):

AUDIT RESULT: CRITICAL FAILURE

Element: Hero tagline "Scan. Crawl. Match. Report." Foreground: ~#C8FF00 (lime green) Background: ~#F5F2E8 (beige) Calculated Ratio: ~1.5:1 Required (large text): 3:1 Required (normal text): 4.5:1 Status: ❌ FAILS BY 2-3x

RECOMMENDED FIXES: 1. Darken text to #5A7300 (olive) → 4.8:1 ✓ 2. Darken text to #3D5C00 (dark olive) → 7.1:1 ✓✓ 3. Keep lime, darken BG to #3D3D3D → 8.2:1 ✓✓ 4. Use #1B5E20 (dark green) → 8.4:1 ✓✓

Checklist for New Designs

Before shipping:

All body text has ≥4.5:1 contrast All large text has ≥3:1 contrast All form borders have ≥3:1 contrast All icons conveying meaning have ≥3:1 contrast Placeholder text is readable (≥4.5:1) Focus states are clearly visible (≥3:1) Links are distinguishable without color alone Error/success states use icons, not just color Tested with color blindness simulators Automated accessibility scan passes

Philosophy: Beautiful design and accessibility are not mutually exclusive. High contrast can be striking, dramatic, and intentional. Low contrast isn't "minimalist"—it's exclusionary. Every unreadable word is a user lost.

color-contrast-auditor

安装