In Norwegian Forest Cats, the Amber gene lightens the black colour. Cat which are black at birth, becomes brighter until they finally appear almost amber or cinnamon during the first year of life. The black colour is retained only at the tips of the tail.
The mutation responsible for the Amber phenotype (e) is located at the extension-locus (E) which controls the generation of pheomelanin also in other species.
Display of the Amber coloration depends on the presence/absence of dominant Orange. In the absence of Orange, males and females with genotype e/e will have the Amber coloration. Amber males that have the Orange gene will be red. Amber females that have one copy of the Orange gene will be amber/red tortoiseshell. Amber females with two copies of the Orange gene will be red.