Just Color Picker - Free portable colour picker and colour editor for web designers, photographers, graphic designers and digital artists. Supports Windows and macOS.
Colordot for iOS - A color picker for humans.
Swatches - A fun and accurate color picker for the real world
Lumu Power - Turn your iPhone into a professional color and light meter.
Pickr - Flat, simple and hackable color picker.
delicolour - GUI application used to choose colours