I could be wrong but it has always been my understanding that TRUE fog lights were yellow and driving were white. Yellow aids in foggy situations due to the color ( white in fog can easily bind ). If you think about it...white FOG lights wouldnt make much sense with this in mind. White lights are designed for clear weather and are supposed to project light WAYYYYY down the road, similar to your high beams but with a narrower path. I think the problem over the years is companies like APC name products FOG or DRIVING lights to sell merchandise and the true useage and naming conventions have gotten mixed up. I am no expert and like I said...I could be wrong but I am getting OLD and the above is what I have always been told.