D 100% Colorless. The highest color grade a diamond can receive. D graded diamonds are extremely rare and very highly priced.
E,F Colorless. Exceptionally transparent. Extremely difficult to detect the traces of color in an E or F graded diamond. These diamonds are rare and highly priced.
G,H Nearly Colorless. Unless these diamonds are compared next to a master stone of higher color grade, color is nearly indiscernible. When face up these diamond appear nearly colorless. These diamonds are still rare, but slightly less expensive and are considered a good value.
I,J Nearly Colorless. Color in these diamonds is slightly detectable. The slight amount of color is imperceptible by the unaided eye once the diamond has been mounted. These diamonds are of superior value, and therefore compose the majority of diamonds that are used for engagement rings, earrings and pendants.
K-M Faint Yellow. Noticeable color, although some diamonds in this range can still be fiery and beautiful.
N-Z Very Light or Light Yellow. Noticeable color. These diamonds are not fit to be sold as gemstones, unless you specifically would like to have a diamond with an amber color.