It doesn't state anything about the light source, it can be a candle if you want, so long as it illuminates suffeciently and gives a decent beam pattern it passes, colour does come into it though.
A mot examiner cannot fail something for being illegal, just because it is or maybe, mini(new sort) had a problem despite having E marked rear lights on some of the aftermarket ones they were still failing mot due to colour of the light.
I have fitted aftermarket, my advice is if the glass comes off/unclips the light on your car, clean the lenses on the inside, as this makes a world of difference I found.
I had to do this on a car due to several bulbs exploding in there was full of glass, and escaping gasses etc tinted the inside surface of the lens, so I cleaned this one, the other I saw no need, until I drove down the road, the pattern from this is awful, but the one I cleaned sharp as anything.
OE hid are much better as they are generally projector lights, ire pattern is formed inside light unit not on front glass.
The reason it becomes a problem is due to it amplyfying the stray light that from a normal bulb would not cause a problem as it is so dim, but of course it reflects this too.
I am going to be taking the HID off, as the philips extreme bulbs are on dip nearly just as good, but streets ahead on main beam, where the H4-4 I have are crap.
tabetha