Source for custom tail lights
 

Sorry for this basic question.

Yesterday I was up on Melrose in LA and I saw another X5 with tail lights that were blacked-out somehow. Not like smoke, but they almost appeared to be coated with something so they were black - except when the lights underneath came on. I've also seen completely clear ones, while on the 405 freeway.

Who sells this stuff? Does anyone have experience with these sorts of mods?

Thanks!