Question

Why is the sky orange and red at sunset

Answer 1

Here ya go ;)

Small particles of dust and pollution in the air can contribute to (and sometimes even enhance) these colors, but the primary cause of a blue sky and orange/red sunsets or sunrises is scattering by the gas molecules that make up our atmosphere. ... In this way, clouds act as a screen on which nature's colors are painted.

Answer 2

At sunset the light from the sun grazes across the surface of the earth, passing through a long column or pathlength of atmosphere. During its passage through the atmosphere the blue components of the light are reduced in intensity, making the transmitted beam of sunlight more yellow or even red in color.

hope this helps ^^