Just because something looks like something does not mean it is that that thing. Genotype (genes) and phenotype (physical appearance) can be different. For example a bird can be solid white. But you would not know whether it is Recessive or Dominant White until it was test bred. Mauve is Blue and Chocolate acting in a combined effort to dilute Black.
All I was trying to say is they look similar. And when you try to do research on it all that comes up for Orpingtons is Dun looks and acts like recessive white. I have to keep these chicks banded because as a new hatch they're identical to my Mauves. Okay next question, why are they hatched looking mauve instead of like a white Orpington?