Gee, I think I might have used a filter a time or two in my 30+ years of photography... I also studied physics of light and optics as an adjunct to my other university studies. I think I have a fairly good understanding of what filters do.
Originally Posted by Noble
Anyway, all flippancy aside, I think we are saying fundamentally the same thing; I just think you have missed the gist of the OP's original post.
And yes, the blue sky is from scattered blue light, but in a transmission spectrum of water or clouds or fog, you will find that the longer wavelengths are absorbed more, resulting in a higher color temperature (i.e., more blue).
The original question was about "enhancing" fog, not "eliminating" it. I agree, that a yellow or red filter will do exactly what you say it will. And, a blue filter would do just about the opposite, i.e., lightening and "enhancing" the haze; that is, making it more apparent.
Note that there is a fundamental difference between shooting a scene with haze in it that is otherwise lit with "normal" sunlight and shooting from within the fog (which is what I believe the OP was addressing). Use of a blue filter in this case will just overexpose the film a bit, since the factor for the filter is not based on the color temperature of the light coming through the fog. It will no appreciably enhance the foggy effect.
Hope this clears things up,