Although most diamonds appear white, the less color a diamond has, the more rare and valuable it is. The best diamonds are completely colorless. That's why diamonds are rated on a color scale from D-Z, with D having the least color and Z having the most. Diamonds can also come in "fancy" colors like blue or yellow. These are very rare and very expensive.

Color grading from totally colorless to light yellow.The differences between one grade and another are very subtle as can be seen by the number of grades within any one category.