I forget to say this splash. blue cop they lay pretty dark eggs 6/8 good shape too Oval . some shiny other flat
they and the cuckoo lay the darkest eggs in the farm. so they are marans ,but what variety?
I am assuming the hen in the picture is supposed to be blue and not blue copper.
the hen in the picture carries one blue allele (gene) and only one (or none) gene called melanotic. She should have black neck hackles- if she had two melanotic genes her hackles would be black. If you mate her with a black male she will produce some blues. She does have a flaw because she should have black neck hackles and crossing to a male that has black hackles will produce some offspring with black hackles.
I would find a black male that does not have any red or white in his plumage. Mate him w ith the hen in the picture. This cross may produce blue birds with the proper color; it all depends on if you hatch enough chicks. If you hatch 20 chicks you should get some properly colored birds. To ensure the best genetic out come, back cross the best blue female offspring to the father. The blue offspring from the back cross should have very good color. blue and black from head to tail.
If she is a blue copper- then she should have red in her hackles.
I am not familiar with the american standard of perfection for marans; if the standard calls for feathered legs then the bird does not meet the standard. As far as breeding it will not be a problem, feathered legs in Marans is normally caused by a dominant gene. The inheritance of shank feathering is more complicated than a single locus and to keep things simple, it is best to think of feather shanks in the Marans to be due to a dominant gene.
I would use the non feathered legged bird as a breeder if it has good plumage color, type, egg color (in females), etc. You are pretty much limited with the birds you have and to make the best from what you have I would breed the bird.
Assuming the birds are purebred for leg feathering, if you cross a purebred bird with a bird without leg feathering then the offspring will have leg feathering. If the cross produces some birds without leg feathering, then the parent with leg feathering is not purebred or other genetic factors are causing the results.