In most other GUIs, the color is applied in a localized and specific sense, either in individual icons or specific control areas, such as window borders or title bars. In the desktop, color is pervasive, as virtually everything is drawn with colors, with a notable absence of black lines.
Most of the icons in this environment use color sparingly, preferring grays instead. This limited use of colors keeps the number of colors used from the palette in the desktop to a minimum and works well visually. Because the icons, being largely colorless, always appear in the context of colored backgrounds, they stand out more.