You mean Type R style? imo leave it unpainted. The cost of painting will be more than it's worth. In terms of looks though, if you can get a perfect colour match then spray it. Most likely it'll look off, which is why unpainted is a safer option

Good luck trying to get it to fit properly. I would have just got the genuine SiR lip for an extra few bucks straight from Honda, they look nice unpainted on any colour.