yeah, I was the one who did those tails on Jonathons car. I got the idea from a writeup on SF...forget who wrote it. Anyways, I used black plastic paint ON THE INSIDE of the lens to create a different light pattern (was looking for a more modern look for the old 2 piece tail set). You could certainly use a smoke tint in the same way and smoke the whole lens or only part of it.
Painting on the inside requires a delicate operation of taking the tails apart without cracking the lenses, but I could give ya some tips if ya decide to do it. Also painting the inside leaves the lenses looking like a dark red or even burgundy look, but still leaves the lenses looking factory on the outside. (meaning they dont look "painted" just different)
I chose the double circle look with three stripes for the turns..but painting on the inside leaves you with only your imagination to stop you from doing something to your liking. I played with three horizontal stripes, and even some stipes at 45 degree angles (like this --> \ \ \ ) but decided on a more traditional look.