painting mach's will not effect light output, due to having projectors. we do quite a bit of work on painting lenses, and the only time you run into issues with degradation of light output is when you have a customer who wants the actual headlight bowls for halogen bulbs painted. we only suggest doing so if you do not intend to use those particular lenses for night driving.
however, like i said, in your case, you will not have issues with visibility after painting.