These rules might change for local towns/cities, but I believe these would carry through out the state.
I chatted with an IMPD Officer (Indianapolis Metropolitan) just this last weekend and asked him about some legal lighting issues I was informed about when looking to buy blue light bulbs for clear side markers. Basically you can't use Red, Blue, or Green in any external lighting, including under body, unless done for show purposes off the roadways. These colors are reserved for emergence personnel only. You should be able to pull off blue lighting in the interior of the vehicle as long as no of the lighting is projected behind or in front of the vehicle. So basically, you can't put anything in the upper half of the vehicle that would be one of those three colors. Purple, yellow, and white are basically your only colors of choice on exterior lighting goes that is visible by everyone.
I was asking due to the fact that I was going to use blue light bulbs in clear side markers and was informed by the person at AutoZone that was illegal in the state of Indiana to have blue lights on the exterior of your vehicle. So, on the way home, I stopped next to a cop that was sitting on the side of the road and asked him. He said it was in a gray area and would be a 50/50 chance that you might get pulled over if a cop had seen it being used. Their is no distinct ruling, according to his cheat book that contains the short hand version of that particular law ruling. If you use clear and clear for side markers and get pulled over for it, explain the following and you should not get a ticket: "The old Lincoln town cars used to use white lights on the side of the vehicle so when the turn signal was used on that side of the vehicle, the light would come on and show the roadway to the right or left so you didn't run over the curb." The cop said that would be the understanding to why clear/clear is a legal color for a side marker.