Just found out that due to the wavelength of yellow light, it does not refract and reflect as much as pure white light would. Since fog/mist/rain is composed of many water droplets that can reflect and refract light, the more there is the less affective white light would be in lighting the road. As such, HID's are generally less affective in the fog/mist/rain and that's why they were equipped with yellow fogs from the factory, whereas the normal filament headlights had normal (non-yellow) fogs.
Just a point of interest I wanted to share.