Much like polishing aluminum, you can also polish plastic. Can't remember the name of the buffing compound, look at www.eastwoodco.com under buffing. I have done this to my taillights and it makes them look as new as they are going to look for being 30 years old. Really, they come out with a nice shine. Just remember you are buffing plastic, so don't leave the buffing wheel in one place for a very long time and if you already have buffing wheels that you use for aluminum, get another set of wheels for doing plastic.
take the lights out and clean all the paint off of them. then paint them with a testors candy apple red (use the paint that is transluscent) then spray about 3 coats of testors clear coat and wet sand for an incredible shine. i did it on my honda to get rid of the amber in the tail-lights and it looks really good.
use wenol metal polish. blue tube. i've always used it on plastic and it works great. works wonders for the plastic headlights on most new cars too. crap lasts forever too. http://superiorcarcare.net/wenmetpol.html