pascalorg Contrast Check
Check color pairs against WCAG 2.1 contrast requirements. Pass in hex colors and get contrast ratios with AA/AAA pass/fail results for both normal and large text.
When to Use
- Checking if a text color is readable against a background color
- Auditing an entire color palette for accessibility compliance
- Verifying colors extracted from a design meet WCAG standards
How It Works
- Takes a list of hex colors as arguments
- Computes the contrast ratio for every foreground/background pair
- Tests each pair against WCAG 2.1 AA and AAA thresholds for normal and large text
WCAG thresholds:
- AA normal text — ratio >= 4.5:1
- AA large text — ratio >= 3:1
- AAA normal text — ratio >= 7:1
- AAA large text — ratio >= 4.5:1
Usage
bash <skill-path>/scripts/contrast-check.sh <color1> <color2> [color3] [color4] ...
Arguments:
- Two or more hex colors (required). With or without
#prefix.
Examples:
# Check a single pair
bash <skill-path>/scripts/contrast-check.sh "#1a1a2e" "#ffffff"
# Check all pairs in a palette
bash <skill-path>/scripts/contrast-check.sh "#1a1a2e" "#e94560" "#ffffff" "#3d83f7" "#bdbdbd"
Output
{
"pairs": [
{
"foreground": "#1a1a2e",
"background": "#ffffff",
"ratio": 16.57,
"aa": { "normal": true, "large": true },
"aaa": { "normal": true, "large": true }
},
{
"foreground": "#e94560",
"background": "#ffffff",
"ratio": 3.94,
"aa": { "normal": false, "large": true },
"aaa": { "normal": false, "large": false }
}
],
"summary": {
"totalPairs": 2,
"passAA": 1,
"passAAA": 1,
"failAA": 1
}
}
| Field | Type | Description |
|---|---|---|
| foreground | String | Foreground (text) color |
| background | String | Background color |
| ratio | Number | Contrast ratio (e.g. 16.57 means 16.57:1) |
| aa.normal | Boolean | Passes WCAG AA for normal text (>= 4.5:1) |
| aa.large | Boolean | Passes WCAG AA for large text (>= 3:1) |
| aaa.normal | Boolean | Passes WCAG AAA for normal text (>= 7:1) |
| aaa.large | Boolean | Passes WCAG AAA for large text (>= 4.5:1) |
Present Results to User
After checking, present a table:
Contrast Check Results:
#1a1a2e on #ffffff — 16.57:1 — AA: Pass — AAA: Pass
#e94560 on #ffffff — 3.94:1 — AA: Fail (normal) / Pass (large) — AAA: Fail
Summary: 1/2 pairs pass AA for normal text, 1/2 pass AAA.
Flag any failing pairs and suggest fixes (darken/lighten the color to reach the threshold).
Troubleshooting
Invalid color — Colors must be valid hex values (3 or 6 digits, with or without #).
Pairing with image-analysis — Extract colors from a design with the image-analysis skill first, then pipe the hex values into this skill to audit accessibility.