What colour is the inside of a panthers mouth suppose to be? I noticed today the inside of my 5 month old panters mouth is green. I tried to find some pictures on line but I can't. I have never seen inside of their mouths before so I am unsure if this is suppose to be the colour or not. He is now starting to get mature and now opens his mouth and tries to bite you when you aproach him so that is how we saw it. He is fine in every other way.