Their is a lot of information about lighting and what is the best. Basically the color spectrum around 3000k to 4000k is the best for visibility. Yellow is the easiest color for the human eye to see so yellow headlights are the best. Also known as French headlights as they were mandatory in France for a long time. Blue is the lowest wavelength on the color spectrum so blue light is the lowest lumen output and is the hardest on the eye to see. Blue headlights actually REDUCE visibility on the road. All those ricer kids who think 8000k headlights are cool are in fact very uneducated and dangerous.
A lot of people purchase cheap HIDs witch do not have a cut off feature preventing glare into the eyes of oncoming drivers. People believe these to be brighter and better but infant their simply dangerous. If your going to buy HIDs make sure they are good quality brand name headlights. Not just cheap xenon bulbs.
More information can be found by searching for Daniel Stern Lighting. I can't remember the URL at the moment but his we page has tons of information about headlights.