Use a common theme among related icons. For example, if you are designing icons for an application, have purposeful similarities between the application's icon and icons for data files.
Be sure the two-color version of any color icon you design is acceptable. If the icon is displayed on a monochrome or grayscale display (or if there are not enough colors available), the icon is automatically displayed in its two-color form.
To conserve system color usage, try to limit icon color use to the colors provided by the desktop. (Icons created using Icon Editor will be use only desktop colors.)
For the sizes used by the desktop components, see Table 14–1.
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.