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.
On other laboratories’ reports
HRD Antwerp grades on the same letters, from D, colourless, to Z, which it calls tinted colour, also by comparison with master stones. It names D “exceptional white +”. The US Federal Trade Commission’s jewelry guides say that when a seller states a grade, the grading system it comes from should be disclosed.
Read next
- Next in Diamond gradingBlue white (diamond term)An old trade term for a diamond’s color, now limited by the FTC to stones that show no color other than blue or bluish.
- The same shape in Smoke and CO alarm soundsLow-frequency 520 Hz alarm (sleeping rooms)A fire alarm in a sleeping room that sounds a low buzz in place of a high-pitched beep. It is the three-beep fire alarm rhythm at 520 Hz, which NFPA 72 requires of alarms provided to wake people in sleeping areas.
More diamond grading
The same shape elsewhere
Browse symbols drawn with letters and numbers or lines.
Sources
- Diamond Color (GIA 4Cs), Gemological Institute of America
- Diamond Quality Factors (GIA), Gemological Institute of America, Color
- The 4Cs (HRD Antwerp), HRD Antwerp, Colour
- Guides for the Jewelry, Precious Metals, and Pewter Industries (16 CFR Part 23), 16 CFR Part 23 (1 January 2021 edition), Federal Trade Commission, published by the U.S. Government Publishing Office, § 23.1, note 1
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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