@Gaialeonmark2 I was looking into what the color was, and Eimi has what’s considered a moss green. Meaning it could be a deep or dulled green when mixing with Izuku’s eyes for Nicholas.
For Natsuyuki and Fuyuharu, there may not be a problem, because Miyuki has relatives who naturally have blue, red, or purple shaded irises. Same might be said for Akahoshi’s magenta, because Honoka has a purple shade for eyes.
Then we have Hanamizu, it could either be red orange as slightly inherited trait from Touko, or we could find a mix between her probable orange or red and Izuku’s green if it’s not brown as a result. But Natsuyami, through Ayako’s red, maybe the heterochromia is a trait that shifted from mother to child?
