Or behind the mountains in the west. You take all that out and the rest Couldn't be anything else but blue. You can see it's true. This is an amusing way to explain why the sky is blue, but it is not true, of course. The sky really gets its colour from the sunlight passing through the air.
Sunlight contains all the colours of the rainbow.
These coloured light waves are scattered as they pass through the air. The blue light waves are scattered most. On a clear day, the particles of gas in the air scatter the blue light. It is reflected into our eyes from all parts of the sky. So the sky looks bright blue.