Interesting I always thought it was wired. I got them from a backyard breeder who had a splash rooster 4 black hens and 2 blue hens. So I just assumed the colouration came from the splash. Here is a photo of all the hens if you could tell me your input. View attachment 2890136View attachment 2890137
Splash doesn't have anything to do with it. Splash is what happens with a bird who is homozygous for the blue gene (sorry, my knowledge of chicken genetics is limited and I can't explain further).
Any red/gold indicates that it's not pure Australorp. Likewise the yellow in the feet -- Australorps have white skin.
HOWEVER, Production Blue crosses are likely to be CHAMPION layers. What I've heard about them is that they're hardy and vigorous. I don't own one, but I haven't heard a bad word about them.
You have very beautiful birds.