Eye Colors Explained! Dr. Allen ranks the rarest eye colors in the world and explains what causes them! Eye color is determined by the amount and distribution of melanin in the iris, the colored part of the eye. Melanin is a pigment that also gives color to our skin and hair. The amount of melanin present in the iris can vary, leading to different eye colors. The most common eye colors are brown, blue, and green, while less common colors include hazel, gray, and amber. There are even some unique eye colors such as pink, violet, or black, but usually, these eye colors are due to other diseases and conditions. The rarity of certain eye colors can also be influenced by genetic factors and the intermixing of populations over time. Additionally, environmental factors such as sunlight exposure can affect the production of melanin in the iris, leading to subtle changes in eye color.