I painted a cake using airbrush colors, but I have to finish it somewhere without them. Can I use regular paint to finish it? It's mostly just details, but I need to know if it will mess up the fondant or anything like that..

If by "regular paint" you mean regular food color gel, (or dust) yes. Usually you would mix the color with lemon juice or a clear alcohol (vodka) then paint it on the fondant.

Nope, I mean acrylic or watercolor paint.

No, you can not. You can ONLY use food colors as suggested by spuddysmom. And I am curious. When you say that you used airbrush colors, do you mean regualr paint colors or did you use food colors?

I think I should have mentioned that it's a styrofoam cake and just for display. I'm not seriously going to paint a real cake with that!

So happy that you cleared that up

lol, in that case... if no one's eating it... paint away with whatever I'd say

I'd choose the watercolor. The acrylic won't give you the food color look. IMO acrylic will look too plastic like.

I have used acrylic with great esults for dummy cake

fondant holds up to acrylic paints?  I have a dummy cake that I need to be gold, but I don't want to spend all that money on edible lustre sprays...I thought I might try spray paint from home depot or acrylic paints on top of the fondant...