Color grades are based on how close a diamond is to being completely colorless. The more colorless it is, the more rare and valuable it will be.

D
Completely colorless. These diamonds are the most beautiful, valuable, and rarest to find.

E-F
Colorless. Slight instances of color are only visible to an expert grader under magnification.

G-H
Near-colorless. Color is not obviously noticeable but can be seen by expert graders under magnification.

I-J
Near-colorless. These diamonds often represent good value but slight traces of color could be noticeable.

K-Z
Faint color to light shades of yellow. Distinct colors, like yellow and pink, are graded on a different scale.