Indiana code specifically states that a person who is not a member of a volunteer fire department may not display an illuminated blue light on a vehicle. Many modern vehicles increasingly use HID (high intensity discharge) headlamps, which project a bluish hue as part of their normal operation. Factory installed HID headlamps are approved by the U.S. Department of Transportation for highway use and do not violate state law.
HID headlamps are superior to traditional halogen lamps in terms of visibility. The lamps come from the factory pre-focused and adjusted not to shine above a certain height (thus reducing the chances of blinding an oncoming motorist). Since the full energy of the light is so precisely focused, under certain circumstances a vehicle equipped with HID lights can subject an approaching motorist to glare. This typically occurs only when the approaching motorist is lower than oncoming vehicle equipped with HID headlights (such as at the crest of a hill).
The National Highway Traffic Safety Administration (NHTSA) is studying the issue of HID headlight glare. You may wish to direct your concerns to their website at www.nhtsa.gov.