I tried the Polarg yellow H1 foglight bulbs. Were ok for a while, but the coating started to burn odf. The old yellow bulbs used cadmium glass for the yellow tint, but now it's banned for occupational health reasond. The coatings don't seem to stand up for long term use.
I got a bunch of Hella Yellow Star before the price went up.
Very nice yellow to match with my OEM HID headlights.
I got it from http://www.rallylights.com - quite pricey @ $6.14 but better than overpriced PIAA.