Philips blue vision bulbs, go for around a fiver on eBay, powerbulbs give a free set when you buy other bulbs off them, I've used them for years now and have changed cars before I've needed to change the bulbs
I tried the Osram Cool Blue ones which weren't quite as white as the headlights but better than the standard ones.
Strangely enough though there was a promotion offer when I bought them so I got a free set of white/blue sidelights that actually matched perfectly! Looks like the promotion is back on again: link
They've got some cheap silver indicator bulbs too, which is must for those with clear side repeaters.