There is a special pray paint that u buy, its about $30-45 buks depending where u buy it from.
thats gonna be the cheaest way.
the other is taking it to a body shop and having them sprayed.
were talking about 100-150 bucks.
http://www.advancespeedshop.com/aug-lens-spray-paint-smoke-p-689.html
15.99 is the cheapest Ive seen this product go for. same brand, same bottle goes for like $50 bukz sometimes.
when u smog your lights you loose visibilty. add aftermarket LED taillights and they shine bright right thru the darkest smog out there.