I noticed the "color of background" of my sim & of the cat, while my sim is feeling playful the cat has the color of felling "fine". Notice the bottom pic has the same color as "fine".
Not sure what you're getting at, but sims portraits and the background color always match their mood. Pets can be orange as well as the colors mentioned by DoloresGrey.
That's what I was trying to say, I was hoping the pets didn't have as many emotions. I've seen the green, the smoky color (which I think is "fine") the dark color when the pet is asleep. Last nite I finally seen the red, didn't think the pet was angry, but knew something was wrong.
I've seen green, orange and neutral grey for pets so far. I like the different colours because I think that if my pet's colour box is orange, it means my pet is sad and needs something.