At the time of sunrise, sun is near the horizon, sun rays have to travel through a larger atmospheric distance. The fine particles present in the atmosphere, having size smaller than the wavelength of visible light, scattered the blue component and other smaller wavelengths present in the components of sunlight. Only red colour having longer wavelength and least scattered, reaches our eyes, hence the sun appears reddish early in the morning. This phenomenon would not be observed on the moon due to absence of atmosphere on its surface due to which sunlight will not scatter. Therefore, the sun does not appear reddish early in the morning.