Diamond Colour Actually Means Lack of Colour
The diamond colour evaluation of most gem-quality diamonds is based on the absence of colour. A chemically pure and structurally perfect diamond has no hue, like a drop of pure water, and consequently, a higher value. GIA's D-to-Z diamond colour-grading system measures the degree of colourlessness by comparing a stone under controlled lighting and precise viewing conditions to masterstones stones of established colour value.
GIA's diamond D-to-Z colour-grading scale is the industry's most widely accepted grading system. The scale begins with the letter D, representing colourless, and continues, with increasing presence of colour, to the letter Z.
Many of these colour distinctions are so subtle that they are invisible to the untrained eye; however, these distinctions make a very big difference in diamond quality and price.
Diamond Buying Guide: Carat Weight
Diamond Buying Guide: Clarity
Diamond Buying Guide: Cut