Green

Kuina learned quickly to look out for green hair because it meant a duel.

A rush of adrenalin.

A green-haired boy that didn't shrink back to fight her again and again and again.

It didn't matter how often she hit Zoro on his mop of unruly green hair; he always came back to rechallenge her.

And Kunia woke up every day awaiting the moment the green-haired boy would fight with her again.

Because the green-haired boy turned into her only true challenge remaining in her father's dojo.

So, Kunia was always looking out for a glimpse of green hair.