RGB, otherwise known as red/green/blue, is a color identification method used by digital computer monitors. Every color gets its own RGB value, and this is because a mixture of those three colors makes up the color you're looking at.
RGB values may be used for a variety of reasons, but mostly for those that do a lot of photo editing or who may be tinkering with graphics or web design.
A little-known feature of your Mac is that its operating system comes with a meter that can identify the RGB color of any single pixel on your screen, and in this tutorial, we'll show you just how that's done.