Skala Color is a compact and feature-rich macOS color picker that works with a huge variety of formats, covering everything you’re likely to need for web, iOS, Android, and macOS development — Hex, CSS RGBA, CSS HSLA, UIColor, NSColor and more.
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.
A simple macOS menu bar app, that allows you to check the contrast ratio between 2 colors and validate it against the WCAG standard.
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.