Originally Posted by Henry H
Yellow lights or yellow film on fog lights have no proven benefit while driving. It does not increase visibility nor "penetrate fog." I don't know when the marketing for yellow fogs came about but any benefits is little to none. Fog lights are just nice and low to illuminate as much of the road while limiting amount of light reflected off the fog (glare).
I believe that I read somewhere that it is in fact the yellow light that is what reduces the glare from fog/rain/snow/what-have-you. But this is just what I came across after researching.
Otherwise, yellow fogs look cool