Grading Color of Diamonds
G.I.A. is the laboratory known for strict grading of diamond color
Since light source and background can have a significant impact on the appearance of color, the diamond's color is graded in a standardized viewing environment. A minimum of two color graders enter their independent opinions into the system. During this phase, the second grader is not privy to the opinions of the first. Depending on the agreement of these opinions, and the weight and quality of the diamond, it may be sent to additional graders who enter independent color opinions. The color grade is determined when there are sufficient agreeing opinions.