Diamond Color

Most diamonds, although appearing colorless, actually have slight tones of yellow or brown. As the tones become more apparent, the rarity and the cost decrease.

The Gemological Institute of America (GIA) diamond color grades:

Before GIA universalized the D-to-Z Color Grading Scale, a variety of other systems were used loosely, from A, B, and C (used without clear definition), to Arabic (0, 1, 2, 3) and Roman (I, II, III) numbers, to descriptive terms like "gem blue" or "blue white," which are notorious for misinterpretation. So the creators of the GIA Color Scale wanted to start fresh, without any association with earlier systems. Thus the GIA scale starts at the letter D. Very few people still cling to other grading systems, and no other system has the clarity and universal acceptance of the GIA scale.