I'm doing this as a joke, I have no idea if this would actually be how their kids would work.

Todomomo

So. We're going off my headcanon for Momo's mamasita and papi.

Mama Murielle has blue hair, Her dad has black. So Momo with the dominant gene Black will be Bb.

Todoroki with half and half will have bb because Rei and Enji showed up like the rat and rat's amazing wife they are. And white=blonde or sm and red is recessive like blonde.

    b  b
B  Bb  Bb
b bb.  bb

Two kids would have black hair (my headcanon)
Two kids would have split or one of todo's colors I guess. Twins and an older sibling?

Kamijirou

We've seen her parents and not Kami's. Since I'm pretty sure blonde can only happen if both parents have blonde hair (might be wrong-) , Denki is bb and Kyouka is BB since Purple is gonna be Black in this case.

  B B
B BB BB
b Bb Bb

Kamijirou could only have kids with purple hair which I don't like >:c

Midotsu

Why did I even bother-

It's green-

IidaMei

Iida has blue only in the family. Dominant in this case BB. Mei has pink. We're gonna say Pink is red.

  B    B
b Bb Bb
b Bb. Bb

So their kids could only have blue hair. The kid might be able to have pink haired kids if it has a pink haired spouse?

Kirimina

WELL WHOOP DEE DOO IM STUPID-

black and Pink/red

With whatever Mina is, that might be Dominant so I'm not going to do that. One kid could be black haired and pink. The other can be pink haired and pale skin :) the end.

Well um.

Scientists, I'm sorry, I learned this is school last year and just remembered this and that's how I make my fanbabies-

So ummmmmmm

I've probable done this wrong. Lololololololol maybe not. I passed Science with an A (we don't get A+'s in my school) so maybe I did it right.

Why would a scientist be reading this tho-

Lololololololol