Join Date: Sep 2006
Car: 2004 Facelift 75 Connoisseur 1.8 turbo with DD Pack. And remember, the troof is out there.
I believe the MOT regulations - if that's what's relevant to your query - state that headlamps should emit white or yellow light (from a yellow headlamp), although some lamps will display a blue tinge (a range of colours is also seen at the periphery of the beam from long distance), but it must be essentially white. This spectral effect is typical of HID lighting transmitted through a projector lens, but isn't the same as a lamp producing essentially blue light. That contravenes the rules. I guess in some cases of doubt, it would be down to the MOT tester's opinion. HIDs at 6000K are acceptabe though they are considerably bluer than the default 4300K most OEM lamps come with. This is a luminance issue rather than light colour. The non-HID projector bulbs fitted originally by MGR were Philips Blue Vision. I suspect this reflected the growing fashion for bluish tinged light rather than any technical advantage.
The description of '6000K' for filament bulbs is misleading IMO. It's more a marketing thing than a true representation of the light quality. However, the addition of xenon gas in filament bulbs improves whiteness and this has evolved a marketing stance that these filament bulbs are 'Xenons' (aka HIDs). I personally wouldn't recommend fitting headlamp bulbs of higher wattage than stated in the Handbook. They will run much hotter than standard, with potential consequences. They may also be a reason for MOT failure.
Lorries seem to get away with anything around Christmas, but some seem to make a year round exhibition.