Few Hues, Many Values

I ran across this excellent excerpt from O'Reilly's Designing Interfaces book about graphic styling of controls and complete GUIs.

It describes an important design decision of a color pallete for your GUI, which is later translated to a full graphic implementation by using the chosen hues with value variations. This can lead to a more coherent design that has only a few chosen hues, and avoids a confusing "rainbow" look.