I had a set of the halford bulbs with the blue ring part of the bulb, couldn't see a thing.
I had a extreme bulb blow whilst on hols in good old Scarborough, bought a cheapie bulb from a £1 shop in town, seriously could hardly tell the difference between that and the extreme, the bulb was a totally blue colour to look at but real white hid loking light with perfect pattern!!
tabetha