I went "over there" and read how I redid my taillight on the Red.
I didn't even take the taillight off the first car I did and it was the "Red" the first Reatta I bought and now have for 13 years. Here's what I did;
Buy 1 quart of Gloss Spar varnish and two 2" foam brushes [May not need the second foam brush
Tape off the letters using painters "Blue" tape or "Frog" tape.
Sand with 1000 grit wet/dry sandpaper
Wipe down with a wet rag
Sand with 2000 grit wet/dry sandpaper
Wipe down with a wet rag to clean the taillight.
Check the tape on the letters to make sure they are in good shape, otherwise remove and apply again
Blow the taillight with air to be sure everything is dry and the dust is removed
Tape off the areas you DON'T want the varnish applied including the reflectors on the bottom of the taillight
Stir the varnish [do not shake] then apply the varnish with a foam brush. Do not over brush, let the varnish level itself off. If you miss a spot refill the brush and hit the skipped area. After you have applied the varnish [shouldn't take more then 5-10 minutes] with a brush with varnish in it do a quick light sweep from end to end to make sure you pick up any "sags" in the already applied varnish.
Allow to dry overnight. That's it.
You will not believe the "pop" you get from the amber tint that is in every quart of Spar varnish. The definition seen in the reflection is almost unbelievable.
Never treat your taillight different with any aftermarket specialty item. Just wash the taillight just as you wash your car. Wipe with a towel as you wipe down your car. Will last for years with minimal care.