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I believe the sheen is genetic and will pass on. Purple sheen cannot be made green no matter what you feed them or how you keep them. I have crossed purple sheen to green and find it often results in both sheens on the bird. I try not to use the purple ones. ("Beetle Green" is desired.) According to Sigrid Van Dort, the presence of Ar+ (Autosomal red) will enhance the green sheen. The purple sheen suggests ar (the absence of Autosomal red). Melanisers are responsible for the green sheen so you might find a BCM cock with a purple sheen gives you more copper on his daughters. Might be worth trying ....
Hmm... so this might be the genetic explanation for what I've read (cannot relocate the source) that old-time Java breeders would keep a few birds with some auburn hackle feathers in their flocks in order to help maintain the green sheen?
Makes sense to me. I imagine they had to be very careful which auburn hackled birds they used. Probably had to be sure they were careful avoiding anything resembling a purple sheen to be sure they were getting all the melanisers they were after so their black stays black. (I've heard it said that presence of an extreme beetle green sheen on the Black Copper Marans suggests over-melanisation and is often connected to a lack of copper on the females so there are obviously different ways for the red to express on a black bird.) Black, it seems, is not entirely straightforward!