Some sanctioning bodies get a wee bit stuffy about that..so check first..For example if someone gets mad and throws his helmet in SCCA you just bought a new one as the one that was thrown is considered damaged and unusable. Painting or modifying any safety related gear is frowned upon in some areas..
Is it fair..well maybe not but that is the rules..
So do a bit of checking..
I have tried most all of it and now do what is known to work..