From Critical Matter:
Color Picker Pro is a small drag and drop savvy application that aids in finding hex, RGB and HSL color values for use in CSS and HTML production. Pull colors out of application windows, icons, your desktop or anything else that you happen to see on your display. Copy or drag and drop color values to your favorite text based CSS or HTML editing application. Store your frequently used colors, undo and redo color changes or make your colors web-safe at the press of a button. Tailor the format of your hex, RGB or HSL color values to your personal specifications. Float Color Picker Pro above other applications and even capture or copy colors while running in the background.