WHY DOES THE GIA COLOR GRADING SYSTEM START AT D?
The GIA universalized color scale has been uniformed for many years. Many grading scales have been used in grading a diamond’s color – an A-B-C scale, an Arabic Scale using 1-2-3, and a Roman scale using roman numerals.
To avoid confusion, GIA chose to start their scale with ‘D’ in order to disassociate from grading scales used in the past. This scale is universally accepted all over the world.
Are there different scales other than GIA? What about after ‘Z’ color scale?
As you access a diamond’s color, separate from the grading, the color scale is divided into five categories from Colorless, Near Colorless, Faint Yellow, Very Light Yellow, and Light Yellow. As you pass the ‘Z’ color grading, diamonds begin a ‘Fancy’ grading scale which includes many different colors.