This is regulated by your state's transportation code. Most states have reserved blue as an "emergency" color so it's a bigger no-no than something like green. I stopped by the police station and made a few calls to find out what I could and couldn't do as far as interior lighting, and the response I got was that it couldn't be a distraction to other drivers, and this decision would be solely from the officer that decides to pull you over. You could go to court and show whatever you have ins't a distraction, but if you got a jerk cop, it would still be a huge hassle.

Blue angel eyes would probably be a distraction, and I know in many places (if not all) headlights (including fog lights I would think) can only have a certain amount of blueness to them and they can test it with a special kind of meter.