Wash the trim with water and a mild detergent. Clean off the the dirt, grease and other debris that have accumulated on the rubber trim.
Remove the old layers of silicone dressing with a spray conditioner and color. The old layers of dressing result in discoloration. Spray the rubber trim with the conditioner and then wipe it with a clean rag or cloth. It may be necessary to repeat the step. Allow the rubber trim to dry after you have finished.
Restore the color and protect the rubber trim against further UV damage with a rubber protectant. Purchase a product such as Pinnacle Rubber and Vinyl Protectant or 303 Aerospace Protectant. Spray the protectant on to the trim. Wipe the trim dry with a clean cloth.
Dye the rubber trim with a rubber dye if the discoloration is too severe to restore with a rubber protectant. Use a product such as Forever Black. The bottle has an applicator tip. Hold the bottle upside down until the tip is saturated with the dye. Apply the dye systematically to trim in a smooth and even fashion.
Wipe off areas around the rubber trim with a wet towel to remove any dye that inadvertently gets on them. Examine the trim. Apply an additional coat of dye if needed.