Originally Posted by 2GreenAutos
Fog lights are intended to light the roadway under the fog. They are indeed effective if they are aimed correctly. I have passed so many people with aftermarket fogs that are aimed high its ridiculous. I do like to use mine as cornering lights or ditch lights also.
Regarding yellow light and fog:
Go down to paragraphs 5 and 6
In bad weather condition where the "visibility" is poor the human eye can see further through the fog with the yellow hued light because our eyes can see that color much better.
This is also the reason many people where glasses with tinted yellow lenses for other uses such as target shooting, gaming, heavy computer use, and many other things. because it allows the eye to work better without as much effort or strain.
And here is the actual evidence of the tests