In addition, the legbar has a barring gene, which makes the black alternate in lines with the red (which in her case, has been diluted to cream by yet another gene). It's not super obvious in females, since they don't express a lot of black, but is more obvious in males, especially their hackle/saddle feathers.
The barring gene mostly makes white lines across the feathers (obvious example: Barred Rock), but the lines are much less obvious on some other colors. I agree it does seem to make a different effect on the colors of a Legbar than on most other birds with the barring gene.
Comb types:
The pea comb gene is considered incompletely dominant. One pea comb gene and one not-pea gene (P/p+) will often produce a comb like Mama A the white Easter Egger has. Two pea comb genes (P/P) will usually produce a pea comb that is smaller and tidier, typically found in breeds like Brahma and Ameraucana and Dark Cornish (but not the white Cornish Cross meat chickens-- it's been bred out of them.) I have seen some pea comb heterozygotes (P/p+) that looked almost like frostbitten single combs: standing up like a single blade, with no points on top. They were a little thicker than normal single combs, but not by enough to be very obvious.
Two pea comb genes (P/P) will also make the wattles smaller, as compared with birds having other comb genes. Muff/beard also makes the wattles smaller.
The pea comb gene and the blue egg gene are also linked (close together on one chromosome, so they are usually inherited together.) The linkage can be any possible combination:
pea/blue egg (Ameraucana)
pea/not-blue egg (Brahma)
not-pea/blue egg (Cream Legbar)
not-pea/not-blue egg (Speckled Sussex, most other common breeds)
If Mama A the white Easter Egger has one pea comb gene and one blue egg gene, there is a good chance they are linked. That would mean that pea-combed chicks from her would lay blue or green eggs and not-pea-combed chicks from her would lay brown/cream/white colors of eggs.
If Mama C has a single comb and lays blue eggs, then obviously she has the linkage of not-pea comb with blue eggs.
...cushion (not sure on the genes for that yet) and rose combs...
Cushion should be R_ PP
Rose comb is considered completely dominant, so you cannot tell which birds are RR or Rr except by test mating or knowing their ancestry. Since pea comb is incompletely dominant, you will typically see a larger comb on birds with Pp, which means a proper small cushion comb is PP not Pp.
The good news is your wyandotte and chanteclers should help you breed in the rose/pea/cushion comb genes that you're looking for. You just want to avoid rrpp, which would give you single combs vulnerable to frostbite. Of course, it will be hard to breed out completely, because of the recessives, and could always pop up in a subsequent generation.
Pure RR PP may be difficult to get, but R_ PP should be much easier. That would let occasional pea combs pop up, but no single combs, so probably not a big problem as regards frostbite.
...wondering if Mama A actually has a cushion comb...
I'm pretty confident that she doesn't. Rose combs are much wider than single combs, with pea combs having an in-between width. Cushion and walnut combs get the extra width of a rose comb, and she does not seem to have that.
That's about as far as I've gotten in my reading. I'm starting with a lot of single combs, but if I keep track of who's carrying it (which is everyone right now, until I replace Papa), I don't think it will be difficult to breed toward homozygous RR and/or PP. Especially if I "tested" a bird with a single-combed mate. But anyway! Except for wondering if Mama A actually has a cushion comb, I think I've got the comb stuff figured out now. On to color and patterning!
