Diamonds that ranges from colorless to light yellow fall within the normal color range. The diamond color scale starts with the letter D and ends with Z. D-colored diamonds have the least amount of colors while Z colored diamonds have the most color. As diamonds are closer to D on the measuring scale, the more expensive they will be. Beyond the Z color, diamonds are graded as Fancy Color, which uses a separate set of parameters.
For a diamond to be more precious, they must reflect all the shades of color. Any color tint in the diamond will obstruct this. Thus, the less color there is, the more will it reflect other shades of color. Colorless diamonds are very rare. They contain little to no impurities and are essentially chemically pure. As the diamond shows more tint of color, it goes down the color grading scale.