In early morning, the sun is at the farthest distance from earth surface. When the white light from passes through the earth's atmosphere, light with smaller wavelength (blue) gets scattered from the dust particles in the atmosphere and only red light reaches the human eye lens. Thus the sun appears red in early morning.
Due to scattering of blue light / light of shorter wavelengths, light of longer wavelengths / red component of light reaches our eyes. This gives reddish appearance of the sun.
