I can't tell scale from this pic, is it one of those little ones you can get out of a vending machine? If so it may be small enough for a betta to push around, but I've never tried it so I can't say. The color should be fine, some bettas are picky but others don't seem to care at all.
My concern would be material safety- if the paint rubs or flakes off is it going to pollute the water? Ay idea what the rubber is made out of? I'd let it soak in a bowl of water for a few days to see if it gets weird or anything (Smelly, cloudy water, warped rubber, etc). Personally I don't think the risk is worth it, but that's up to you to decide.