Phaeomelanin is responsible for the yellowish-blond to red colors and Eumelanin is responsible for the brown to black shades. 棕黑素形成亚麻色到红色发质，真黑素形成棕色到黑色。
Both animals and humans have phenotypic variations of eye color that are attributed to ratios of eumelanin, a substance produced by melanocytic cells in the iris. 动物和人都有眼睛颜色的表征变化，这是由于真黑素含量不同造成的，真黑素是虹膜中的黑色素细胞产生的一种物质。
