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?
The Myths of Color Contrast Accessibility
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
Accessible Color Generator
Contrast Rebellion - to hell with low-contrast fonts!
Low-contrast font color and unreadable texts? To hell with them!