[Tatsfield]

I think there is a real difference between ancient technology coloured headlamp glasses and the colour temperature of light emitted by HID lighting systems. Light in the area of 4500° is white but tinged yellow. 5000° light is bright white but tinged blue and 6000° is much more blue. 4500° is probably the nearest to standard halogen bulbs but much brighter while 5000° is what a lot of factory fit units emit. 6000° is what is generally favoured by the owners of garish modified hot hatches. Units emitting light in excess of that in the purple range seem to be used by motorbikes who's owners have a death wish anyway!