Originally Posted by sunamer

Blue light gets scattered more easily by water (or water vapor also), which basically makes fog glow uniformly while not letting that light through to the obstacle you are trying to see while driving through that fog. Yellow light is a bit better, because it does not get scattered that easily.

1. Also, understand that K number is a certain point on the mathimatical (warmer...........neutral............more blue) line, and it does not represent a particular single wavelength. If you wanna know more about what K is - read about black body spectrum.
https://en.wikipedia.org/wiki/Black-body_radiation
Basically, there is no such thing as “pure” white light. White light is the “dirtiest” “color”, and in reality is a mix of different visible wavelengths (true pure colors). The first chart on that page I just gave you shows what K actually means. You can see that the more overall spectrum is shifted toward shorter wavelengths (blue), the higher K will be and more blue it will appear to the eye. The same applies to the warm colors, but the spectrum needs to move to longer wavelengths and have more of those in order to be perceived as “warmer” white.

2. The reason blue light is useless for us for night driving is because human eyes have the highest sensitivity in greens. Blue sensitivity of a human eye is 3-20 times less than that of the green part of the spectrum, which is why using head lights of 9000-15000K is stupid. Whoever does it, unknowingly limits his own chance of seeing something on the road before it is too late.