Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
Just Color Picker - Free portable colour picker and colour editor for web designers, photographers, graphic designers and digital artists. Supports Windows and macOS.
ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
Instant Eyedropper - Identifying the color code of an object on the screen is usually an involved, multistep process:...
LightShot - The fastest way to take a customizable screenshot.
gcolor2 - GTK+2 Color Selector