Why does bluish colour predominate in a clear sky?

The molecules of air and other fine particles in the atmosphere have a size smaller than the wavelength of visible light. These particles are more effective in scattering light of a shorter wavelength at the blue end than the light of the longer wavelengths at the red end. The red light has a wavelength 1.8 times greater than blue light. Thus, when sunlight passes through the atmosphere, the fine particles in the air scatter the blue color more strongly than red color. The scattered blue light enters our eye and we see the blue color of the clear sky.