The color of external mucous membranes is always black as the presence of eumelanin prevents the formation of cancers in the exposed tissue. These features are always black regardless of the genetic pigmentation present in the individual. All black membranes are:
- Eumelanin is a dark pigment that is deposited in both hair and skin. In mucosa surrounded by eumelanin-derived hair color, eumelanin is also present in the mucosa, which turns the blue to a darker shade of purple. Therefore, a grey individual would have purple mucus membranes.
- Pheomelanin is a red pigment that only effects the hair color. Therefore, there is no pigment in the internal mucosa and the skin is colored by hemocyanin only. An orange individual would have blue mucosa as pheomelanin would not impact the skin.