Do you know why the sky is blue?
That's a great question, why is the sky blue?
It is blue because of an optical effect known as Rayleigh scattering. 
Can you describe this optical effect more?
Scattering is light particles that we can see, and blue is the shortest and fastest meaning we see it more.
So this means there are also other colors in the sky, but we just see blue?
Correct. And when we see different colors, it is because additional particulate matter scatters as well, usually at dusk or dawn.