A purple sheen does not mean there is anything wrong with a bird or nutrient deficiency. Its simply what color refraction you see. I have a bird that I see a purple sheen on that 6 people have said they can't see the sheen. A sheen color is in the eye of the beholder and some of it depends on the lighting. If my hair is shiny it doesn't mean I'm sick. It means my hair is healthy with plenty of vitamins and nutrients. Dull hair means damage and maybe needs a wash. Feathers aren't much different.
Didn't mean to stir the pot. I did some research into sheen and it looks like the late Geneticist Dr. Clive Carefoot stated that his theory on the purple barring is that is is caused by irregular feather growth due to poor nutrition, ill health, etc. There may be some people that confused purple barring for purple sheen because most of what I am finding confirms that sheen color is more likely due to genetics although one report did confirm that stressing bird that didn't have purple sheen previously can get it.
I found a comparison of Hatchery Australorps to Show line Australorps and on the same feed the show line had the sought after green sheen and the hatchery line the purple sheen.
I also found that one breeder selected for red sheen in Black Chabos.
So selection either way will improve sheen color one way or another. The recommendation is to never cross a purple sheen with a green sheen if you want to maintain your green sheen though. Once it is in the line is hard to get out.
One source indicated that purple sheen is caused by too much black in a mating so in the in black varieties the birds with purple sheen also have a tendency to completely black legs, completely black beaks, and mulberry colored combs.
Birds that were carrying recessive color patterns were reported to have less green sheen that those that with out recessive color patterns. Birds with white in the wing tips where reported to have more green sheen.
Observation on sheen with respect to silver bases, gold bases, mahogany, and autosomal red were also noted.
Edited by GaryDean26 - 11/20/15 at 12:57pm