On that basis these is an internationally accepted scale for color, indicated by the usage of the latin alphabet letters in scale from D to Z. Rules are very simple: the whiter the stone, it is marked by a letter closer to the initial letter of the alphabet. The similar rule applies for diamond values: fewer colors means higher price.
Diamond color is graded by comparing a sample stone to a master stone set of diamonds. A trained diamond grader compares a diamond of unknown grade against the series of master stones. This process occurs in a lighting box, fitted with daylight equivalent lamps. Also, accurate color grading can only be performed with unset diamonds.
