In TEXAS Any lighting device mounted on the REAR of the vehicle must reflect RED, or if it is a SIGNALING DEVICE it can be RED, AMBER, or YELLOW. (not white, blue...)
A TURN SIGNAL lamp shall emit WHITE or AMBER light if mounted in the FRONT of the vehicle. (Not blue, red...)
A vehicle lamp that projects a beam with an intensity brighter than 300 candle power shall be directed so that no part of the high-intensity portion of the beam strikes the roadway at a distance of more than 75 feet from the vehicle.
I believe underbody lighting is legal if you use AMBER or WHITE and there is no glare.
Basically, only white and amber in front. Red, white, and amber in back. As for HID lights, Aim them so they hit less than 75 feet in front of your car.