Contrast
A macOS app for quick access to WCAG color contrast ratios → https://itunes.apple.com/de/app/contrast-color-accessibility/id1254981365?l=en&mt=12
Perceived brightness: an essential concept for UI design
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?
Pika
… an easy to use, open-source, native colour picker for macOS. Pika makes it simple to quickly find colours onscreen, in the format you need, so you can get on with being a speedy, successful designer.
Accessible Color Generator
Color.review
Colors that look and work great for everyone
Designing UI with Color Blind Users in Mind - Secret Stache Media
In Plain Sight
ColorSafe
Empowering designers with beautiful and accessible color palettes based on WCAG Guidelines of text and background contrast ratios.
Colour Contrast Check
For people with impaired vision, we are required to ensure that there is a minimum amount of contrast between our foreground and background colors. formulas for determining optimum color contrast. W3C's specification on color contrast... hp color palette. style sheet text colors. style sheet text colors.
Contrast Rebellion - to hell with low-contrast fonts!
Low-contrast font color and unreadable texts? To hell with them!