Indigo ~ symbol (In)
Indigo is an autosomal co-dominant modifier .
The heterozygous form of Indigo (i.e., only one gene in the bird) shows a sort of bronzed /rusty red colour on the pattern areas ,and turning the smooth spread areas into an an andalusian blue colour . Indigo also washes out the tail bar so instead of being black the tail bar is lighter than the rest of the tail .
The homozygous form (i.e., two genes in the bird) mimics ash red, so a homozygous indigo could easily be mistaken for a mealy or a red cheq ,although the rump and neck is normally a darker Indigo hue than is found in ash-red birds.