The term “color” is very important, but it is misleading–because the ideal diamond is characterized by a lack of color. The color tinting found in most diamonds is caused by minute impurities within the stone.
The color of each diamond is determined by comparing it to authenticated “master” diamonds. Each stone is then color-graded to a precise scale from “D” (colorless) to “Z” (Saturated).
Colorless diamonds are extremely rare.