Fog lamps aren't supposed to be less output of light, just a warmer color and lower to the ground. The bluer the light the more it scatters and when dealing with fog you have enough scatter already. So you can put in yellow HID, add 12 more and you'd be great - in fact better than stock. The halogens are pretty warm color already, by going with a blueish white of normal LED or HID you lose effectiveness for their intended purpose. Though honestly I've not had to use fog lights for fog more than one time in over 20 years now. Normally I consider them driving lights and love the way they spill light onto the sides to illuminate shoulder etc. So color is irrelevant.