Turbo-Tint tail light spray.

R-Tec do it http://www.rtecshop.com/index.php?p=browse&category=80

Or call them on 01727 790100. Remove the lamps from the car and clean them up with warm soapy water and make sure they are bone dry and free from grease and crap before starting. Apply lots of thin coats allowing time for each coat to dry before adding the next. Once at the required tint use a cutting polish to give a nice finish and then re-fit to the car. Bobs your mothers brother