color-convert

Parse the hex string into integer RGB channels, then use the colorsys module's rgb_to_hls function to get hue, saturation, and lightness values. The Skill provides ready-to-use hex_to_rgb and rgb_to_hsl functions with validation for 3-digit and 6-digit hex formats.

Compute relative luminance for each color using the sRGB linearization formula, then divide the lighter luminance plus 0.05 by the darker plus 0.05. WCAG AA requires 4.5:1 for normal text and 3:1 for large text, while AAA requires 7:1 and 4.5:1 respectively.

OKLCH is a perceptually uniform color space where lightness changes feel even to the human eye, making it better than HSL for generating color scales. Use it for modern CSS theming with hex fallbacks, but note that some OKLCH colors clip when converted to sRGB.

Yes, OKLCH conversion requires the coloraide package, installed via pip install coloraide. Basic HEX, RGB, and HSL conversions work with only the Python standard library's colorsys module.

Perceived readability differs from computed luminance contrast, especially for mid-tone grays and pastels on white. For example, #94A3B8 on white yields only 2.56:1, failing AA; darkening to #64748B raises the ratio to 4.68:1 and passes.