The Federal Department of Transportation / Traffic and Highway Safety also your state regulatory agency such as DOT or DMV can weigh in on the subject. Most states prohibit the use of blue lights on the front of any vehicle not a law enforcement vehicle.
You can put blue film over your headlights but you can not change the lights to be blue. It is illegal. Only emergency vehicles can have blue or red lights.
It is illegal to have any light that oscillates or revolves in yellow, red or blue. If your blue headlights don't do those things then you are good to go.
"Blue Moon Detective Agency"
If you buy blue xenon bulbs they are easily fittable to headlights on most car designs. Any mechanic should be able to do it or you can also do it yourself. If you take it to a mechanic bring the bulbs with you.
Animals' eyes show up different colors in headlights. A deer might have green or blue eyes in the light of the headlights. Cats can show up different colors also, ranging from a bright yellow, to blue or green. Opossum eyes are usually red in headlights.
Daniel Stern Lighting and Thumper Talk are both sites that advertise for this product. Blue headlights are available on Amazon and they include pictures to see them.
They are in the state of Ky and I suspect they are in every state.
HID headlights are far more brighter than normal Halogen bulbs that are normally in headlights. HID are often thought of as safer because they have a blue glow to them and resemble daylight more than normal bulbs.
Not usually, but you can tint your headlights red (NOTE: This is against the law)
UNESCO
Argentina
Low beams are the headlights when they are dipped. Used to light up the road just in front of you and biased towards the kerb nearest you. They also allow you to be seen clearly, but without blinding oncoming vehicles or those in front of you. When there is no other traffic to blind, the headlights should be switched to main beam, to give you the best view ahead and early warning of dangers. A blue light on the dashboard warns you when your headlights are on Main beam and blinding. If you have your headlights switched on and there is NO blue light, then your headlights are on Low beam.