General blue light is very poor to see by and is why blue head lights are illegal. The police will eventually do you for them. You can get road legal bulbs with a very slight blue hew to them but then tend to be quite dull. Philips and Osram so legal bulbs but there white bulbs are far superior. Philips have a bulbs called “BlueVision” That is a road legal bulb that looks a lot like stock xenon bulbs you get in many cars these days. There “Xtreme Power” is much brighter but is more white in colour. Just stick to a good name and you will be fine. Some of the unbranded stuff for sale on Ebay is just pure junk.
“HID KIT” that are simply a bulb are all illegal as they are not safety rated. The people selling them are generally speaking conmen. The truth is These kits can NOT be DOT approved. They can NOT be E approved. Philips do NOT make such kits. Osram do NOT make such kits. Bosch do NOT make such kits. Hella do NOT make such kits. Such kits are NOT road legal. Your insurance company will NOT cover a none legal car. This is the governments official fact sheet
http://www.dft.gov.uk/pgr/roadsafety/drs/hidheadlamps this web site also has good info
http://hid.moonfruit.com/ This is also a good one to look at
http://www.youtube.com/watch?v=yVuSSdZNsZw