Colored diamonds form under the same conditions as clear diamonds, but their colorations are due to chemical impurities or structural imperfections within the crystal lattice. Although all diamond color varieties are possible in nature, some are easier to replicate within a laboratory setting than others.
Colorless diamonds are the rarest of all types. Scientists officially recognize 27 different diamond colorations and class them within three broad groups. Type I diamonds derive their colors from nitrogen impurities and include those that are mostly clear, yellow or brown. Type II diamonds result from structural defects and can be red, pink or deep brown. The final group, which includes green diamonds, becomes colored as a result of radiation exposure.