[pulvinar]

I like the idea of all-around-visible brake lights, but also think they should be red only.

The problem with green on the front is that cars stopped at a light at night will be presenting a green light to oncoming traffic that should also be stopping, possibly overriding the red traffic light or stop sign.

[Ancapistani]

Green is also the only color, to my knowledge, that isn't commonly restricted for accessory lighting. The laws governing strobes and sirens are written broadly enough that they cover any light that you could possibly make blink, even if you don't do o.

In most US states blue is for police and red is for fire. Some states let other vehicles, like tow trucks, use blue. Sometimes they'll use blue and red for police - but blue is always restricted to my knowledge.

Yellow/Orange/Amber is for "caution". Some states restrict that and some don't, but it has an understood meaning.

Purple signifies a hearse or funeral procession.

I learned about these laws in the early 2000s, when I was in my late teens and early twenties and wanting to drive a customize minitruck. It turned out that in my state, all colors of strobes and accessory underlighting were restricted... except green.

What's worse is that the law specifically includes a provision where possession is considered to be sufficient evidence of use. Technically it's illegal to buy a battery-powered toy with an LED strobe in it, if you drive home with it within reach of the driver.