Im not a bodybuilding judge but I don't see how it wouldn't negatively affect your scores. If you look like shit you're gonna look like shit, tattoos or not. But if you're in great shape and your in a tight contest with another guy who's in great shape but not covered in tattoos; I think it is a lot easier to see the definition, quality etc.
I mean skin tone plays a part. Thats why having an even tan is important. Having a bunch of big blotchy marks all over your body can't be optimal in a contest judged on appearance. But again, im not a judge.