This rating describes how much color a diamond has in it. Because colorless diamonds sparkle more than others, they tend to be more valuable. The scale on which jewelers rate diamonds is alphabetical, with D being the most colorless and valuable, and with Z having the most color and least value. Diamonds with clarities of D, E or F have essentially no color, and those with G, H and I have little to no color that is visible to a non-professional eye.