Marcy, I keep remembering little things from the past so will post as I can. The old Poultry Books and the Old Time breeders always said to use a male in the color you would like the young to end up being. I would use a BC male if he were from a Blue Copper breeding but would not use a BC copper from pure BC. It would be ok to use a BC female over a splash or Lighter Blue Copper male.
We can forget most of the Genetic formulas when it comes to Marans as they are two scattered bred to breed true regardless of how they are bred.