Insider Blog: The colors of the sky explained

The color of the sky is determined by the angle of the sun in the sky (how much atmosphere the light needs to pass through) and how the light is scattered by air molecules in the atmosphere. Since blue light has the most energy of any wavelength of color, it is scattered first which is why the sky appears blue during the day.

At dusk and dawn, the sun is at a lower angle in the sky. This means the light must move through more of the atmosphere. As a result, the blue light is scattered more and the red and orange wavelengths shine. When dust or smoke is present, the light is scattered even more. This allows for an even richer red or orange sky. However, the extra particulates absorb some of the light, meaning the colors are overall dimmed.