One of the rarest of colors in natural color diamonds. … Purple is a dominant and rare hue in nature and color diamonds. As purple color is correlated to internal grain formation, the cut is exceedingly important to color release. So rare are these pure purples, there has yet to be revealed a large, historically important pure purple diamond. The presence of hydrogen will impart a purplish shade to a diamond ranging from light violet tone to a beautiful purplish hue.