Desktop icons use a palette of 22 colors including:
Eight static grays
Eight static colors: red, blue, green, cyan, magenta, yellow, black, and white
Six dynamic colors: foreground, background, top shadow, bottom shadow, select, and transparent
This palette creates attractive, easy-to-read icons without overtaking color resources needed by other applications. Most icons provided with the desktop use grays accented with color.
The transparent color is useful for creating icons that have the illusion of being nonrectangular because the color behind the icon shows through.