The only thing I found in the old (2000) vehicle code book says:
All lamps and reflectors visible from the front, sides, or rear of a vehicle except headlamps, may have any unlighted color, provided the emitted light from all lamps or reflected light from all reflectors complies with the required color. Except for backup lamps, the entire effective projected luminous area of lamps visible from the rear or mounted on the sides near the rear of a vehicle shall be covered by an inner lens of the required color when the unlighted color differs from the required emitted light color.
I can't find anything about tinting the tailights being illegal. I smoked mine on this car and on my old car and never had a problem.