Yellow colour light is used as fog light because yellow colour

Yellow light is preferred for fog lights due to its position in the visible spectrum. According to the VIBGYOR sequence, yellow has a longer wavelength than violet, blue, and green. While Rayleigh scattering affects shorter wavelengths more significantly, making blue light scatter easily, longer wavelengths like red, orange, and yellow scatter less and penetrate fog more effectively. Red has the longest wavelength but is strictly reserved for brake and stop lights to ensure safety and standardization in automotive signaling. Orange is often avoided for fog lights because its spectral proximity to red can cause visual confusion for other drivers. Therefore, yellow is the optimal choice as it offers a long wavelength for better visibility and penetration through haze while remaining distinct from the colors reserved for critical safety functions like braking.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 10: The Human Eye and the Colourful World > Activity 10.2 > p. 167