Mutations resulting from changes to eumelanin production or expression
Eumelanin gene mutations, including changes to gene expression or alteration in the production of melanin’s, would lead to mutation-induced melasma.
Eumelanin is another type of melanin that makes black or brown pigments in many animals such as birds.As a result, several mutations could end up affecting eumelanin expression and thus pigmentation which results into different colored birds. Here’s a brief description of the mutations you mentioned: