During sunrise and sunset, the colour of sun appears to be ______ .
red
During sunset and sunrise, the colour of the sun and it's surroundings appear red. During sunset and sunrise, the sun is near horizon, and therefore the sunlight has to travel larger distance in the atmosphere. Due to this most of the blue light (shorter wavelength) is scattered away by the atmospheric particles and only the light with longer wavelength (red colour) reaches our eyes. This is why sun appears red in colour during sunrise and sunset.