Assuming my barred cockerel has one blue gene, and I breed back to a homozygous blue Legbar hen, I would likely end up with some olive eggers homozygous for blue, right? And I could select for duckwing (e+) vs. Extended black (E). It might require some patience, but would be easy enough to spot, since it's recessive. The part that is the biggest mystery, and I can't find any clear research to point me in the right direction, is on the genes controlling the brown overlay. So, I don't know how many generations it would take to eventually get pullets with true blue vs olive. Seems like it could be a fun project with interesting egg colors along the way and shed light on how to breed out brown.