Federal DOT sets uniform regulations. They constantly do studies regarding safety issues ie: study of daylight running lamps on cars had no effect ( increase or decrease) on crashes
States are required to adopt a minimum set of standards and most states laws are that no other lamps may be lit during operation on a roadway. ( white and amber to the front, amber to the front and red to the rear from the side, steady red , flashing red and flashing amber, white to plate and no white to the rear except while backing to the rear)
Some States and Judges within states have different views of a blue HID vs a bluish tint HIS. Officers know their judges, especially senior ones, and typically stay within what a judge will convict you on.
You can have all the red to the rear you want as long as it is not blinding or distracting and it stills allows you to see the required uniform blinkers and brake lights. In Illinois you may only have 4 white lamps lit to the front at a time, very few officers will stop you unless you are blinding oncoming drivers. All the amber you want as long as you are not blinding or distracting. Nothing rotating or flashing ( except for directional) in front Modulators are ok on daylight white lights only. My comment is that if you stay with traditional lights or combinations you may can be as visible as you want without risking being stopped for it.
http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=571.108