Which colour of light is scattered the most (maximum) in the atmosphere?
The molecules of air and other fine particles in the atmosphere have their size smaller than the wavelength of visible light. Thus, they are more effective in scattering light of shorter wavelengths, e.g. blue light. The red light has a larger wavelength than blue light. Thus, when sunlight is passing through the atmosphere, the fine particles in air scatter the blue colour (shorter wavelengths) more strongly than red.