For years (40+) I ran an original single tail light with original lens (yellow on top). I run a 12 volt system.
Last year, I decided to get the reproduction red lens with STOP etched into the top section. Then more recently, I decided to switch to LEDs for all lights except headlamps. I found that running white colored LEDs through a red lens was not satisfactory; only an incandescent bulb would do.
So now I run an LED 1156 style retrofit bulb with red light emitting LEDs together with my original yellow on top lens. Wow! When that super bright red LED lights up it turns the yellow lens bright RED! When not lit, the lens stays the stock yellow!
From superbrightleds.com:
1156 LED Light Bulb with Stock Cover - (36) SMD LED Tower - BA15S Base
Product Code: 1156-R3W-G