What is the true colour of the sky?

Answer 1

The sky is actually colorless. The color you see is actually sunlight being diffracted by the gases in our atmosphere. On a clear (non-hazy, non-polluted) day, the sky appears blue. This is due to the high concentration of Nitrogen. However, in a smog clogged city, the sky can appear white to dirty brown. This is due to the high concentration of hydrocarbons. You can even get a red-orange sky if you're near a large fire or if a large volcano has just erupted.

Answer 2

The true color of the sky is blue due to Rayleigh scattering, which causes shorter wavelengths of light (blue and violet) to be scattered more easily in the Earth's atmosphere. This scattering effect is why the sky appears blue to our eyes during the day.