Most cars in America have, at most, three colors of lights on the outside. There’s white for headlights and reverse lights, red for brake lights and rear lights plus, in some cars, amber for turn signals. Mercedes-Benz has just gotten approval to add a fourth color. Turquoise blue lights indicate when a Mercedes car is driving itself.
My state, too (Indiana, for reference)
I’d go with Purple/Violet. Not a color light you really see anywhere on roadways so it would stick out easier.
Purple is for rain.