Sunsets are red because sunlight must pass through more atmosphere then, and the atmosphere scatters even more light at bluer wavelengths, leaving mostly red light to color the sky.

Question

Quizplus · Accepted Answer

This is because of the scattering of light in the atmosphere, which scatters more blue light than red light, leaving mostly red light to color the sky during sunsets.

Sunsets Are Red Because Sunlight Must Pass Through More Atmosphere