Contrast is a macOS app for designers and developers that provides quick access to WCAG color contrast ratios.
Chameleon is a macOS app that gives quick access to changing the interface, accent and highlight colors from the menu bar. It has a very simple interface, if you've used the System Preferences panel to make any changes then it should look really familiar.
The Perfect App to convert HEX & RGB colors to UI- and NSColor for both Objective-C and Swift. It also features a copy to clipboard functionality.