Fog lights are not suppose to match anything, there where design to cut thru dense fog, so the more yellow they are the better the visibility.Ideal output should be below 4000K.
You might find this useful:
So, what is a good fog lamp? A good fog lamp produces a wide, bar-shaped beam of light with a sharp horizontal cutoff (dark above, bright below) at the top of the beam, and minimal upward light above the cutoff. Almost all factory-installed or dealer-optional fog lamps, and a great many aftermarket units, are essentially useless for any purpose, especially for extremely demanding poor-weather driving. Many of them are too small to produce enough light to make a difference, produce beam patterns too narrow to help, lack a sufficiently-sharp cutoff, and throw too much glare light into the eyes of other drivers, no matter how they're aimed.
Good (and legal) fog lamps may produce white or Selective Yellow light—
it is the beam pattern, not the light colour, that defines a fog lamp—and most of them use tungsten-halogen bulbs though there are some legitimate (and a lot of illegitimate) LED fog lamps beginning to appear. Xenon or HID bulbs are inherently unsuitable for use in fog lamps, and blue or other-colored lights are also the wrong choice.
France was the contry that required yellow lighting and since that was abolished, there has not been any major improvements in yellow as a valid color for fog lights. Interestingly, what is noted is the hman eye, rather than the light, is what reacts to the coloration of the reflected light.
" What explains the persistent subjective preference amongst experienced poor-weather drivers for yellow fog lamps, despite decades of white fog lamp prevalence? Selective yellow light can improve a driver's ability to see in fog or rain or snow, but not because it 'penetrates fog better' or 'reflects less off droplets' as is commonly thought. That effect is known as Rayleigh Scattering, and is why the sky appears blue. However, it occurs only when the droplet size is equal or smaller than the wavelength of the light, which is certainly not the case with ordinary fog, rain or snow. Roadway Fog droplets are several orders of magnitude larger than visible light wavelengths, so there's no Rayleigh Scattering."
So, the choice is just up to the driver. Until headlights are built to fill the entire roadway, edge to edge, auxiliary lighting will be needed. Fog lights will fill the bill here in the US until such time that they allow Driving Lights to be legal. And yes, the low cutoff for white does fill the same bill as the yellow lights. If yellow were the only colow that was acceptable, then why have a red rear fog light...why not amber like the turn signals?
