I cant say I understand how colored furs are different than mice wearing hats and things from anime, games and other things. I mean it never was a game about realism. They're still mice but they've transformed into mice that can have unique coloring that is not native to the species. Sounds legit to me.
Well, everyone likes different things I'm sure if the artist absolutely *hated* them they wouldn't have drawn them out so nicely They did state they prefer the colors over the furs, and that's their own opinion
Some people are going to wish it was only realistic mouse patterns, others love the other animal furs, you shouldn't let it get you sad, it's just a difference in preference
I don't think it means they're personally disappointed in you for adding them or anything :[