Just Color Picker - Free portable colour picker and colour editor for web designers, photographers, graphic designers and digital artists. Supports Windows and macOS.
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
Sip - A better way to collect, organize & share your colors.
ColorSlurp - Pick, edit, save, and copy colors. The best color picker in the universe!