Look at the image above. Don’t you feel some colors are brighter than others? For example, between the yellow and blue: which is brighter?

The APCA Advanced Perceptual Contrast Algorithim SIMPLE VERSION.

The W3C Accessibility Guidelines (WCAG) 3.0 provide a wide range of recommendations for making web content more accessible to users with disabilities. Following these guidelines will address many of the needs of users with blindness, low vision and other vision impairments; deafness and hearing loss; limited movement and dexterity; speech disabilities; sensory disorders; cognitive and learning disabilities; and combinations of these. These guidelines address accessibility of web content on desktops, laptops, tablets, mobile devices, wearable devices, and other web of things devices. They address various types of web content including static content, interactive content, visual and auditory media, and virtual and augmented reality. The guidelines also address related web tools such as user agents (browsers and assistive technologies), content management systems, authoring tools, and testing tools.

Accessible Palette is an app for building color systems with consistent lightness and predictable contrast ratios across color levels.