color-accessibility

Color Accessibility Skill

Purpose

Analyze color palettes for WCAG 2.1 accessibility compliance. Calculate contrast ratios for all color pairs, identify failing combinations, and suggest fixes to meet AA or AAA standards.

When This Skill Applies

• User asks "are these colors accessible?"
• User wants to "check contrast ratios"
• User needs "WCAG compliance" for a palette
• User asks about "color accessibility"
• User wants to ensure colors work for colorblind users
• User mentions "AA" or "AAA" standards

Trigger Phrases

Natural Language	Action
"Check if these colors are accessible"	Full WCAG analysis
"What's the contrast ratio?"	Calculate specific pair ratio
"Make this palette AA compliant"	Analyze + suggest fixes
"Is this readable?"	Text contrast check
"Color blind friendly?"	Color vision deficiency check
"Fix the accessibility of this palette"	Remediation suggestions

Parameters

• --palette <colors> — Comma-separated color values to analyze
• --foreground <color> — Specific foreground color (for pair check)
• --background <color> — Specific background color (for pair check)
• --standard <level> — Target standard: A, AA (default), AAA
• --fix — Include remediation suggestions for failing pairs
• --matrix — Show full contrast matrix for all pairs

Analysis Process

1. Parse Colors

Accept colors in any format and normalize to HEX + RGB + HSL:

• HEX: #1a1a2e, #fff
• RGB: rgb(26, 26, 46)
• HSL: hsl(240, 28%, 14%)
• Named: navy, coral, forestgreen

2. Calculate Relative Luminance

For each color, calculate relative luminance per WCAG 2.1:

For each channel (R, G, B):
  sRGB = channel / 255
  linear = sRGB <= 0.04045
           ? sRGB / 12.92
           : ((sRGB + 0.055) / 1.055) ^ 2.4

L = 0.2126 * R_linear + 0.7152 * G_linear + 0.0722 * B_linear

3. Calculate Contrast Ratios

For every foreground/background pair:

ratio = (max(L1, L2) + 0.05) / (min(L1, L2) + 0.05)

4. Evaluate Against Standards

Standard	Normal Text (< 18pt)	Large Text (>= 18pt or 14pt bold)	UI Components
A	No minimum	No minimum	No minimum
AA	4.5:1	3:1	3:1
AAA	7:1	4.5:1	4.5:1

5. Generate Contrast Matrix

For N colors, generate an N x N matrix:

Contrast Matrix (AA Standard)

           #1a1a2e  #16213e  #0f3460  #e94560  #ffffff
#1a1a2e      —      1.2:1   1.8:1    5.4:1    14.2:1
                     FAIL    FAIL     PASS     PASS
#16213e    1.2:1      —      1.5:1    4.5:1    11.8:1
           FAIL               FAIL    PASS     PASS
#0f3460    1.8:1    1.5:1      —      3.0:1     7.9:1
           FAIL     FAIL              FAIL     PASS
#e94560    5.4:1    4.5:1    3.0:1      —       2.6:1
           PASS     PASS     FAIL              FAIL
#ffffff   14.2:1   11.8:1    7.9:1    2.6:1      —
           PASS     PASS     PASS     FAIL

6. Color Vision Deficiency Check

Simulate how the palette appears under common color vision deficiencies:

Type	Prevalence	Affected Colors
Protanopia (no red)	~1% males	Red-green confusion
Deuteranopia (no green)	~1% males	Red-green confusion
Tritanopia (no blue)	~0.003%	Blue-yellow confusion
Achromatopsia (no color)	~0.003%	All hues lost

Check that colors remain distinguishable under each simulation. Flag pairs that become indistinguishable.

7. Remediation Suggestions

When --fix is specified, for each failing pair suggest adjustments:

• Darken the darker color or lighten the lighter color
• Adjust saturation to increase perceived contrast
• Suggest the minimum lightness shift needed to pass
• Provide the adjusted color value

Failing pair: #0f3460 on #e94560 (3.0:1, needs 4.5:1)

Suggestions:
  Option A: Darken background → #0a2340 (ratio: 4.6:1) PASS
  Option B: Lighten foreground → #ff6b7f (ratio: 4.5:1) PASS
  Option C: Use white text instead → #ffffff on #e94560 (2.6:1) FAIL
            Use white on darkened → #ffffff on #c93050 (4.8:1) PASS

Output Format

Summary View (default)

Accessibility Report — AA Standard

Palette: #1a1a2e, #16213e, #0f3460, #e94560, #ffffff

Overall: 6/10 pairs pass AA (60%)

PASSING (6):
  #1a1a2e on #e94560  — 5.4:1  (AA normal text)
  #1a1a2e on #ffffff  — 14.2:1 (AAA normal + large)
  #16213e on #e94560  — 4.5:1  (AA normal text, borderline)
  #16213e on #ffffff  — 11.8:1 (AAA normal + large)
  #0f3460 on #ffffff  — 7.9:1  (AAA normal + large)
  #e94560 on #1a1a2e  — 5.4:1  (AA normal text)

FAILING (4):
  #1a1a2e on #16213e  — 1.2:1  (needs 4.5:1)
  #1a1a2e on #0f3460  — 1.8:1  (needs 4.5:1)
  #16213e on #0f3460  — 1.5:1  (needs 4.5:1)
  #e94560 on #ffffff  — 2.6:1  (needs 4.5:1)

Recommendations:
  - Avoid using dark colors on each other for text
  - #e94560 needs a darker variant for use on white backgrounds
  - Consider adding a dark text color (#1a1a2e) for light backgrounds

Pair Check View

Contrast Check

Foreground: #e94560 (Coral Red)
Background: #1a1a2e (Dark Navy)

Contrast Ratio: 5.4:1

AA Normal Text (4.5:1):  PASS
AA Large Text  (3.0:1):  PASS
AAA Normal Text (7.0:1): FAIL (need 7.0:1)
AAA Large Text (4.5:1):  PASS

Best Practices

1. Test text on backgrounds, not just swatches — A palette can look cohesive but fail for readability
2. Check both directions — Light text on dark AND dark text on light
3. Include white and near-black — Most palettes need a light and dark neutral for text
4. Don't rely on color alone — Use icons, patterns, or labels alongside color for meaning
5. Test at actual sizes — Large text thresholds are different from normal text
6. Consider dark mode — Recalculate for dark mode backgrounds