I noticed something interesting on a collection of new Fords, and it probably applies to some later model cars of different manufacture.
The color of the tail lamp, brake lamp, directional, etc. can be either from the lens or a special bulb (LED?) inside.
I have red lenses on my TaurusX; these are for brakes. I have clear lenses too--for the directionals WITH amber bulbs. I think they are LED arrays as you can't see the bulb color unless they are on and flashing.
The Mercury Mountaineer has all clear lenses and the color of the braking, tail lamp and directionals are all controlled by colored lamps--not lenses.
Michael Salemi
1969 280SL
Signal Red 568G w/Black Leather (Restored)
President, International Stars Section
Mercedes-Benz Club of America