I wouldn't do red, white and blue, as blue is the one color that is reserved for police/emergency vehicles in every state, as far as I know. In the northeast, like BigDig, the cops will be all over you for even one blue light, including your iPod that can be seen from the road when dash mounted. I know someone who got stopped for that, and then the cop made him move it right there on the spot. It sucks too, because blue is such a cool color and my truck is blue, so I'm stuck with purple if I want to do something close to blue. Not that anything is wrong with purple, I like purple a lot, but blue would look better.
Anyway, all I would dare to do would be to change maybe the left-center and right-center lights to amber, or just the center light to amber, simply for variety.
Whatever you do, don't be too surprised if you end up with the blues (or reds and blues) on behind you some night, especially in Ma. (no offence, but they're pretty bad out of all the northeast states).