The diamond color evaluation is based on the absence of color. A chemically pure and structurally perfect diamond has no hue, like a drop of pure water, and consequently, a higher value. The D-to-Z diamond color-grading system measures the degree of colorlessness by comparing a stone under controlled lighting and precise viewing conditions to masterstones stones of established color value.
Many of these color 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.
Absolutely colorless. The highest color grade that is extremely rare and most expensive.
Colorless. Only miniscule traces of color can be detected by an expert gemologist in a controlled environment, a very rare diamond.
Colorless. Slight color detected by an expert gemologist, but still considered a colorless grade, a rare, high quality diamond.
Near-colorless. Color may be noticeable compared to diamonds of better grades, but offers excellent value.
Near-colorless. Color slightly detectable when compared to diamonds of better grades, a good value.
Slight or obvious color.