Hi, mountain Bourbons,
there are many colors of Marans. the seller didn't tell you what color 'plain Marans" were? maybe she meant cuckoo. the three most popular colors are cuckoo; Wheaten; and black copper. it's possible you can get black copper. I have no idea. The seller should have told you what color a plain Marans was. email them and ask.
On second thought, I wonder if the seller meant they didn't have feathers on their shanks. In other words, they were a plain Marans, not a French Marans. The French Marans have feathers on their legs. that might be it.
If that turns out to be the case, not a problem
if you want feathers on their legs all you have to do is breed the hens to a feather leg Marans rooster. some of the chicks will have feathered legs. it's easy to add them in
Frankly, I like to clean Shanks better, it's less messyif the feathers get wet or muddy.
Here's the cultural history behind The Feathered legs. in France ,the Marans people pasture their Birds on grass .feathers on the legs are not a problem. in England ,the Marans people's yard their birds in poultry yards. the feathers get wet and messed up on the bare ground . so the English people bred the feathers off the legs. they have clean legged birds. earlier this century ,when the two Marans clubs in America vied for APA approval of the breed, there was a big fight about whether there should be feathers on the legs . eventually, the APA went with the French standard and demanded feathers on the legs. if you want to show the birds today, they must be Feathering legged. the English birds still exist and are around .frankly, I like them better if you're going to yard your birds. they do better in wet and muddy weather I think. but you can't show them. if you want to show them ,then you need to breed them to a feather legged rooster . some chicks will have feathered legs and you can show them.
Best,
Karen