In the UK there is very little scope for alternative lamp colours on a car. Blue and Green can only occur on emergency vehicles, amber flashing on indicators, road maintenance vehicles and airports, red not allowed at the front, only red on the rear except the 'standard' uses. There will be an easy to find gov.uk page for the full road vehicle light requirements I'm sure.
As an aside, back in the sixties or seventies before i was driving it was normal for sides and brakes to be 2 different brightnesses of red in the same housing. I think they did some tests with green side lights instead and found reaction times improved dramatically. Presumably they got a good enough improvement from just separating the lights instead and so green was never allowed.