Diamond color is one of the "4 Cs" used to grade the quality of diamonds. Essentially the less color, the higher the price (except for fancy color diamonds). Diamonds that are clear and colorless like water are the most expensive and have a D to F color grade.

The following chart uses the color grades as defined by the Gemological Institute of America (GIA).

Just because a diamond is yellow doesn't mean it is of lesser quality. It is simply worth less because there are fewer natural colorless diamonds and the demand for them is high.

However, fancy color diamonds can be worth a lot more than a colorless diamond. For example, a one-carat natural red diamond can sell for ten times more than a D color diamond of the same quality and size.