Diamonds of all colors can be found in nature. Over 300 colors have so far been identified, however these come in an infinite number of shades and hues.
From pink to black, spanning all the colors of the rainbow including blue, red, yellow, green, gray and brown, natural color diamonds are all excluded from the D to Z classification, which only applies to colorless ("white") diamonds.
Given their diversity but above all their rarity, a specialized nomenclature has been created in an attempt to properly classify, and evaluate the quality of natural color diamonds. Indeed, the criteria by which their quality is judged are very different from those used to evaluate colorless diamonds (the 4 Cs), and therefore their certificates also.