Just Color Picker - Free portable colour picker and colour editor for web designers, photographers, graphic designers and digital artists. Supports Windows and macOS.
ColorSnapper - The missing color picker for Mac.
Instant Eyedropper - Identifying the color code of an object on the screen is usually an involved, multistep process:...
Contrast - A macOS app for quick access to WCAG color contrast ratios
gcolor2 - GTK+2 Color Selector
Pika - 100% ESM. A new kind of package registry that does more for you. Write once, run on any platform.