Because the human eye is most sensitive to yellow light and green light. In fact, the color of the car light has little to do with the scattering factors, because in the case of heavy fog, the degree of Michaelis scattering has nothing to do with the wavelength of the incident light.

When the weather is clear without haze, Rayleigh scattering is related to the wavelength of incident light. The longer the wavelength, the weaker the scattering. In this case, the wavelength of red light is longer than that of yellow light, so it is not easy to scatter, and the penetration of red light is better.

Nowadays, cars are generally equipped with front and rear fog lights. The front fog lamp is yellow or white, and the rear fog lamp is red. In fact, the turn signal is pure yellow. Nowadays, the popular daily LED driving lights are all white, and they are not specially made into yellow or red, so you still don't need to interpret the meaning of the color of the lights too much.