The most prized diamonds are colorless diamonds, because their beauty depends entirely upon their remarkable optical properties. In such diamonds, all the colors of the rainbow are reflected back to your eye. While the majority of Gem diamonds appear to be colorless, others can contain increasing shades of yellow to brown, some of which are referred to as champagne diamonds. Other diamonds of exceptional color, red, blue, green, pink, and amber are known as "Fancies".

The color grading scale varies from totally colorless to light color or tinted. The difference between one grade and its neighbor is very subtle. The absolute finest colorless stone carries a D rating, descending through each letter of the alphabet to Z, designating a diamond of light yellow, brown, or gray. This body color may be caused by the presence of trace elements, such as nitrogen, within the atomic framework of the carbon crystal. These trace elements are so minute that they are scientifically measured in parts per million (ppm). As the body color becomes more intense, the grade for color descends the scale. These gradations are so minute and precise that discerning a single grade (even by an expert) under less than ideal laboratory conditions is extremely difficult. Experts never try to remember color, they use master diamonds of known color for comparison.