Labels. It's been part of the Mac OS since I bought my first one, which came with System 7 on it.
OK, I changed the folder colors in Finder, but if I then move the folder to the Finder Sidebar the color disappears. I downloaded easySIMBL and the ColorfulSidebar Plugin but there's no effect in the window.
I'm running Lion on an intel iMac
I Made some quick icons that are the OSX icons colorised for the Finder labels - Won't work in the Lion/Mountain Lion Sidebar but should be fine in the finder