Not to mention how cool it was following 20+ NSXes down an exit ramp on the way back from RealTime Racing, seeing all those brakes lights lit up.... That's a memory that will last a while.
As for legality, I would see if your state has a website where you can access laws on-line, and find the sections about motor vehicles, and then find the ones talking about lights, and read them. I'd have to check again to be sure, but I'm pretty sure that in Washington there's nothing against it. Heck, according to the law in Washington, you can have amber brake lights if you want. =)
-Mike