The most popular Color for Diamonds is "white" or colorless. Whilst Diamonds come in every Color of the spectrum, for "white" Diamonds truecolorless examples are extremely rare and therefore demand the highest value.
Regular "white" Diamonds are graded by Color and are given letter designations dependant upon how far they deviate from the purest "white."
Put simply, just a small amount of Color can diminish a stone's "brilliance & fire" and therefore ultimately negatively effect the overall value of any given Diamond.
Diamonds deemed to be truly colorless are awarded the Color grading of D. Color grading then continues down through the alphabet, with each letter designating a slightly yellower tint. The progression is:
D : Absolutely colorless. The highest color grade, which is extremely rare.
E : Colorless. These are extremely rare and sought after. Only minute traces of color can be detected by an expert gemologist using a loupe.
F : Colorless. Significant quality stone. Slight color detected by an expert gemologist, but still considered a "colorless" grade.
G-H : Near-colorless. Color noticeable when compared to diamonds of better grades, but these grades offer excellent value.
I-J : These can be excellent value stones. I-J Color Diamonds are almost colorless with only a slightly detectable yellow tint, often making them offer excellent value for money.
K-M: Diamonds with color grades of K through M may appear faintly yellow, brown, or gray in their settings
Recommendation : The best way to determine the true Color of a diamond is by looking at it against a white surface.