I would go with film, a little harder to get it to lay down correctly, but easily taken off and will not fade or show signs of wear like cheap lense paint. You could have them professionally painted, but more $$$ than vinyl film and more permanent. Check my gallery, my car is 20% and it looks like SkyShadow's. I have seen black XFs with 5% film and it looks like there are no tail lights until you hit the brakes. I would go 20% if I were you.

I am in Indiana and asked a cop when I did my lenses and he said they were well within my legal rights. Got pulled over the other day (47 in a 30) and he didn't say a word. Then again, I have some pretty serious bulbs in mine so there are NO issues seeing my lights.