Both red dogs and blue dogs are born white (except for any solid-coloured body or face markings) and the red or black hairs show from around 4-weeks of age as they grow and mature. The distinctive adult colouration is the result of black or red hairs closely interspersed through a predominantly white coat. The mask consists of a black patch over one or both eyes (for the blue coat colour) or a red patch over one or both eyes (for the red coat colour).