The APCA version, to be licensed for use with guidelines: W3/AGWG.

APCA (Accessible Perceptual Contrast Algorithm) is a new method for predicting contrast for use in emerging web standards (WCAG 3) for determining readability contrast. APCA is derived form the SAPC (S-LUV Advanced Predictive Color) which is an accessibility-oriented color appearance model designed for self-illuminated displays.

Check the contrast between different colour combinations against WCAG standards

Inspect the contrast in color combinations, making sure to comply with the accessibility guidelines established by WCAG.

Get the contrast ratio and WCAG score between two colors in order to ensure accessibility

Core components for iOS and tvOS to accelerate building user interfaces in code.

♿ Accessible pygments themes

[Mirror] Tempus is a collection of themes for Vim, text editors, and terminal emulators that are compliant at the very least with the WCAG AA accessibility standard for colour contrast

Checks the color contrast of your color design based on Web Content Accessibility Guidelines (WCAG)

Colority it's a PHP library that allows you to: transform and validate colors, obtain the best contrast color (using contrast ratio from WCAG 2.0 standard), extract colors from images and more.

A tool to check for color contrast using APCA

visualizing relative luminance contrast within sRGB colorspace

A color picking tool.

Omnibus Prime is a classic blog starter theme, made using PUXL framework, tailor-fitted for WordPress. Have your stories accessible, WCAG 2.1 AA compliant with zero effort: color-contrasted, responsive, customizable, human and eco-friendly.

[Mirror] Tool to build Tempus themes on demand. Tempus is a collection of themes for Vim, text editors, and terminal emulators that are compliant at the very least with the WCAG AA accessibility standard for colour contrast.

A CLI utility to calculate/verify accessible magic numbers for a color palette.

WCAG accessibility colour contrast checker web extension

SwiftContrast: Color picker with instant WCAG contrast analysis for accessible design.

A tool to check WCAG contrast compliancy of multiple color combinations.

Lea Verou's contrast ratio checker