A grade given to a diamond to describe the subtle tones of Color in a stone. D is perfectly colorless, the most rare and expensive color. As you go from D to Z on the normal color scale, it indicates increasing levels of yellow and/or brown tones. It takes a trained eye under special lighting to distinguish between neighboring color grades (such as E to F), but most people can discern the difference between colors that are several grades apart (such as E to H) with a little practice.
GIA invented the system that is most widely used today all over the world.
Color Grade is one of the Four C’s.
Fancy Colors such as pink, red, blue and green are discovered each year, but they are rare and expensive. Such fancy colors do not follow the normal color/pricing scales and are categorized separately.
Following is a very general outline of the range of color grades ::
The normal color scale, as defined by the GIA ::
D, E, F = Colorless
G, H, I, J = Near Colorless
K, L, M = Faint Yellow
N, O, P, Q, R = Very Light Yellow
S, T, U, V, W, X, Y, Z = Light Yellow
To grade accurately, and consistently with the grade definitions used at GIA, master color grading diamonds (very precisely selected and graded samples from GIA) or Cubic Zirconias are used for comparison, like the one below ::
Here is how I would compare the various grade definitions of the major labs around the world ::