Question

why is the colour of the sun changes while setting

Answer 1

During the sunset, the sun is near the horizon , the light has to covered a greater distance to reach us. during this long journey, the shorter wavelengths blue light scattered away from the our sight, now the only long wavelengths red light is present and we can see the sun appear to reddish

Answer 2

The Sun doesn't actually change colour. It is the position of the Sun relative to where you are that results in all those cool and pretty apparent changes in the colour of our Sun. This lesson will outline for you why the Sun is one colour at high noon and totally something else at sunset.