accessible-contrast

Accessible Contrast Pairs

Generate color ramps specifically designed for accessible text/background combinations. Uses an 11-step scale for predictable WCAG-compliant pairing.

When to Use

• "Create accessible color combinations"
• "I need WCAG compliant colors"
• "Generate high contrast pairs"
• "Make sure my text is readable"

Installation

npx @basiclines/rampa

The 11-Step Strategy

Why 11 steps? It creates predictable pairing math:

Pair	Indices	Contrast Level
Maximum	0 + 10	Highest (near white + near black)
AAA Normal	1 + 9, 2 + 8	7:1+ ratio
AA Normal	3 + 7	4.5:1+ ratio
AA Large	4 + 6	3:1+ ratio

Recipe

rampa -C "<brand-color>" -L 98:5 --size=11 -O css --name=color

• -L 98:5 ensures full range from near-white to near-black
• --size=11 creates indices 0-10 for easy pairing
• Pairs are symmetrical: 0+10, 1+9, 2+8, etc.

Complete Example

For brand color #3b82f6:

rampa -C "#3b82f6" -L 98:5 --size=11 -O css --name=blue

Output:

:root {
  --blue-0: #f8fafc;   /* Near white */
  --blue-1: #f1f5f9;
  --blue-2: #e2e8f0;
  --blue-3: #cbd5e1;
  --blue-4: #94a3b8;
  --blue-5: #64748b;   /* Middle gray */
  --blue-6: #475569;
  --blue-7: #334155;
  --blue-8: #1e293b;
  --blue-9: #0f172a;
  --blue-10: #020617;  /* Near black */
}

Contrast Pairing Guide

For Normal Text (4.5:1 minimum - WCAG AA)

/* Light backgrounds with dark text */
.light-subtle {
  background: var(--blue-0);
  color: var(--blue-7);  /* 0+7 = AA */
}

.light-default {
  background: var(--blue-1);
  color: var(--blue-8);  /* 1+8 = AA */
}

.light-strong {
  background: var(--blue-2);
  color: var(--blue-9);  /* 2+9 = AAA */
}

/* Dark backgrounds with light text */
.dark-subtle {
  background: var(--blue-10);
  color: var(--blue-3);  /* 10+3 = AA */
}

.dark-default {
  background: var(--blue-9);
  color: var(--blue-2);  /* 9+2 = AA */
}

.dark-strong {
  background: var(--blue-8);
  color: var(--blue-1);  /* 8+1 = AAA */
}

For Large Text (3:1 minimum - WCAG AA)

.large-text {
  background: var(--blue-3);
  color: var(--blue-7);  /* 3+7 = AA Large */
}

Maximum Contrast

.max-contrast {
  background: var(--blue-0);
  color: var(--blue-10);  /* 0+10 = Maximum */
}

Quick Reference Table

Background	Text for AA	Text for AAA
0	7, 8, 9, 10	8, 9, 10
1	7, 8, 9, 10	8, 9, 10
2	8, 9, 10	9, 10
3	8, 9, 10	9, 10
7	0, 1, 2, 3	0, 1, 2
8	0, 1, 2, 3	0, 1, 2
9	0, 1, 2	0, 1
10	0, 1, 2	0, 1

Multiple Colors

Generate accessible ramps for multiple brand colors:

rampa -C "#3b82f6" -L 98:5 --size=11 -O css --name=blue
rampa -C "#22c55e" -L 98:5 --size=11 -O css --name=green
rampa -C "#ef4444" -L 98:5 --size=11 -O css --name=red

All ramps use the same index pairing logic.

Tips

1. The -L 98:5 range is crucial - it ensures full contrast range
2. Middle values (4, 5, 6) work for disabled/muted states
3. Always test actual rendered contrast - tools like Stark, axe can verify
4. The index math (0+10, 1+9, 2+8) makes theming predictable
5. For buttons: use index 5-6 as background, 0-1 as text