Couleurs is a simple app for grabbing and tweaking the colors you see on your screen.
Couleurs takes Apple's color panel (complete with "magnifying glass"), and combines it with an easy way to copy common formats of color values to the clipboard (including CSS formats like #rrggbb and even UIColor values in Swift).
You can also copy the color to your clipboard by pressing ⌘C or you can paste any CSS color by pressing ⌘V while Couleurs is active.
Download Couleurs for free
Requires macOS Sierra (10.12) or newer