My rear Turn Signal Lenses were quite faded. I finally fixed them with a few craft store supplies and some patience. The result was excellent. Youd be hard pressed to tell that my lenses are painted. Ill go ahead and outline the fix so it can be used as a reference.
-Supplies needed- I found these at Michael's, but most craft stores carry them. Transparent Glass Paint (Red & Yellow) Perm Enamel Surface Conditioner Clean Paint Brush
-Instructions- Remove your tail light assemblies. Now might be a good time to fix your tail light circuit boards. Clean the surface of the lens thoroughly with warm soapy water and allow to completely dry.
Apply the Surface Conditioner and let dry for a few minutes. Use a large amount of the yellow glass paint and begin adding 1 drop of red at a time until you get the desired color of amber. Be careful not to create air bubbles while mixing.
Make sure your tail light is perfectly level before painting. Paint an evenly spread thick coat onto the the plastic lens. Inspect your work for errors from every angle in good light. Once your satisfied, let the paint dry in a non-humid place for 3 days before reinstalling on the car. Again, make sure the assemblies are laying perfectly level or you may end up with undesirable runs. After 10 days of drying, the paint hardens and becomes waterproof, as well as heat resistant.