Adhesive backed transparent red vinyl.
Clean the surface of the tail light. A little water on the surface of the tail light will allows you to position the overlay properly and move it around if need be. Use a credit card, CVS card, Walgreens card, etc to squeegee out the remaining water. You can use a blow dryer to help dry out the water below the vinyl and start the adhesion process. Allow 24-48 hours for the tint to adhere to the tail light.