Breed identification

[Bertram]

Disagree (sorry @Bertram , i don't mean to call you out specifically yours just happened to be the first post saying this when I scrolled back up) Since single combs are recessive, they can be passed down for generations undetected before they pop up seemingly out of nowhere. Since single combed birds were used in creating the wyandotte breed it's a gene that has, AFAIK, always been present in the breed.

Single combs are more common in hatchery birds because hatcheries are breeding for volume and aren't picky about birds meeting the standard.

As for the blue vs black, this one's tricky. Blue can range from pale Grey to so dark it looks black except that it lacks the green beetle sheen you get with black feathers. I can't tell from these pictures if she's a very dark blue or black.
Even if she is black, that's always a possible outcome of breeding blue because of how the blue gene works. One copy of blue dilutes black pigment to blue. Two copies dilutes it further to black. Since a blue bird has one copy of blue genes and one for black, when you breed two blue birds together some of the chicks will inherit one copy of blue from one parent and one black from the other parent. Some of the chicks will inherit one copy of blue from each parent and be splash. Some chicks will not inherit a blue gene from either parent and will be black.View attachment 4179297
This image I found on a quick Google search does a pretty good job of explaining it visually.

I had forgotten about that, but you're right, that is probably what this is. I actually have a SC Ancona from RC parents so I should have remembered.