WHat is Illegal vs Legal as regards to tinted or painted tail lights?
 

Are Painted GTR Taillights completely illegal????

What constitutes Legal as far as what direction you should go towards tails?

you should look up your local law it will tell you.. or just ask a cop.. most states aslong as the tail lights that light up show red you are good.

Look up FMVSS 108.

I'd imagine any decrease in OEM light output and anything inhibiting the reflector operation would be deemed illegal. I'm sure it really depends how "important" this is to local law enforcement. Similar to window tints, some states or locales let deep window tint slide while others will ticket you on the spot.
I haven't had any trouble w/ the law w/ my painted GTRs and I go across several state lines on a regular basis. I'd say you're much better w/ GTRs (w/ the side marker exposed) then a solid tail tint. My rear light output is nearly the same as OEM FWIW, and I have no tinting on my reverse lighting.

in New York the law is technically that you must be able to see the lights from 300 feet away in daylight.

In any case GTR style is the way to go. looks much better than completely black anyway.