I've used the spray on tint and it faded fast... taillights look stock again. One thing I have seen done is to paint a candy paint over the light, this acts like the smoked taillight covers that you would put on with tape, but these don't come off (if done right) and you can tint it any color you want. Candy paint is just clear coat with a very same amount of color. I saw this done one an NSX and some other imports it looks pretty nice.
