D-to-Z color scale
The letter grade for a diamond’s color, from D for colorless to Z for light yellow, brown or gray.
How to read it
GIA introduced the D-to-Z color scale in 1953, and started it at D to avoid confusion with the systems that came before. The normal color range runs from D, colorless, to Z, light yellow, light brown or light gray. At GIA’s laboratory a stone’s color is graded by comparing it with masterstones of known color, under controlled conditions.
Also searched as: D color diamond, diamond color chart, diamond color scale, G color, H color.
Grades describe a stone as a grading laboratory saw it. This page explains the grading scales; it doesn’t grade or value any stone.
Why does the scale start at D?
To avoid confusion, comparison or association with earlier systems, GIA begins with D as the top, colorless grade.
Is D better than H?
D is less colored. GIA explains that colorless diamonds are scarce, most having tints of yellow or brown, so a colorless diamond rates higher than a light yellow one.
More diamond grading
Sources
- Diamond Color (GIA 4Cs), Gemological Institute of America
- Diamond Quality Factors (GIA), Gemological Institute of America, Color
Last reviewed September 27, 2026 by Rory Hansen. How we research