Just Color Picker - Free portable colour picker and colour editor for web designers, photographers, graphic designers and digital artists. Supports Windows and macOS.
gpick - A color picker and color scheme creation tool.
Instant Eyedropper - Identifying the color code of an object on the screen is usually an involved, multistep process:...
gcolor2 - GTK+2 Color Selector
PicPick - PicPick screen capture software enable you to grab an image on your computer screen, save, print, add effects, and share.
Sip - A better way to collect, organize & share your colors.