Just Color Picker - Free portable colour picker and colour editor for web designers, photographers, graphic designers and digital artists. Supports Windows and macOS.
Swatches - A fun and accurate color picker for the real world
Instant Eyedropper - Identifying the color code of an object on the screen is usually an involved, multistep process:...
ColorSnapper - The missing color picker for Mac.
gcolor2 - GTK+2 Color Selector
Colordot for iOS - A color picker for humans.