Genetics
The Violet mutation has an incompletely dominant relationship to its wild-type allele. That is, there are three distinct phenotypes, possessing zero (the wild type), one (the single factor heterozygote) and two (the double factor homozygote) Violet alleles, with the heterozygote having an intermediate appearance between the wild-type and the homozygote.
Because the Violet factor is always visibly expressed no budgerigar can be split for Violet. The heterozygotes of Violet — the SF Violet Greens and Blues — correspond to the splits of the recessive mutations.
The violet mutation is autosomal, but it has not yet been determined whether there is a linkage to any of the other budgerigar mutations. There has been a long-held view that the violet mutation was linked to the blue and dark mutations, but this is now uncertain. It seems more likely that the unexpected breeding results which prompted the view were caused by incorrectly identifying birds carrying single and double violet factors. There is no reported measurement of this or any other linkage.
In the past, there was a view that the violet allele was lethal in double factor form, but this is now disproved with many breeders reporting DF violets.
Read more about this topic: Violet Budgerigar Mutation