When the evaluation of a diamond’s color is done it is actually based on the absence of color. Diamonds that are both structurally and chemically pure have zero diamond color hue, like a drop of pure water and thus a have a higher value on the market. The GIA (Gemological Institute of America) uses a D-to-Z color grading system that measures the exact degree of colorlessness by comparing it to another stone under strictly controlled lighting and viewing conditions in order to establish the diamonds color grade.
The GIA’s diamond color grading scale is the industry standard and most widely used diamond color grading system (See above).
Many color distinctions are invisible to the untrained eye, however these distinctions make a significant impact on diamond quality and price.