Wait wait wait. Hold on.
Sena is GREEN?!
Japanese works don't go full furry very often so I tend to forget that Japanese hair rules are still in full effect... wherein there is no such thing as an unnatural hair colour.
It was weird enough learning that her hair is "sky blue", but apparently Sena is GREEN. Still not sure if he is a fox or a jackal or what, but being GREEN is something that never even occurred to me because it is SO COMPLETELY FUCKING WEIRD that there is no situation in which I could possibly predict it.
Now I think about it, they said before that Chise is blue. I kinda automatically assumed that by "blue" they meant blue in normal animal fur terms, which generally means a kind of silvery grey. But if Sena is green then maybe Chise is full on sapphire blue.