I'd rather for the meantime they got some Police attention - fitting blue bulbs (or retrofit LEDs) is classed as a modification - and because it's a bit "chavvy" insurance companies really don't like it so most people who have done so are probably not correctly insured. You have to fit the manufacturer's spec, which in an older car is a halogen bulb without a coating.
Though the scourge of newer cars is auto dim/dip, which doesn't dip until they see your lights, so you get momentarily dazzled, whereas a competent driver manually dipped *just before* rounding the corner. They also don't dip for cyclists or pedestrians. I'd ban them.