Ok, the factory painted helmets are probably safe but...
What about the homebrew/custom painted jobs? Aren't some types of paint fairly flammable? I remember a lacquer pot that flashed when hit by grinder sparks.
The other thing,
The plain helmets are ANSI rated based on the material the mfg. used. I also recall some paints/solvents will turn certain plastics into goo.
So how do you know the custom paint on yer lid hasn't, at the least, un-ANSIed it (can't think of a better word), or at the worst, yer wearin' a flare waiting to be lit?