When it comes to diamonds the best color is no color. Well cut stones allow light to be reflected and dispersed in a way that when delivered back to our eye produces a beautiful scintillating rainbow.
However, light dispersion has no effect on the technical grading of color.

The absolute finest colorless diamond carries a D color rating.
These ratings descend through the alphabet to Z, designating a diamond of light yellow or brown.

Color gradations are so minute and precise that discerning a single grade (even by an expert) under less than ideal laboratory conditions is virtually impossible.


Why does the GIA color grading system start at D?

Before GIA developed the D-Z Color Grading Scale, a variety of other systems were loosely applied. These included letters of the alphabet (A, B and C, with multiple A’s for the best stones), Arabic (0, 1, 2, 3) and Roman (I, II, III) numerals, and descriptions such as “gem blue” or “blue white.” The result of all these grading systems was inconsistency and inaccuracy. Because the creators of the GIA Color Scale wanted to start fresh, without any association with earlier systems, they chose to start with the letter D—a letter grade normally not associated with top quality.


In some exceedingly uncommon instances diamonds are found in varying exotic colors like pink, blue, green, amber, and even red. These stones are prized for their extreme rarity and are referred to as “fancies,” their intensity is graded and governed by a different scale than white diamonds.