Why's the sky blue?
The sky is blue because the white light of the sun refracts through the clouds with each color as a different wavelength, and the shorter wavelengths (such as blue and violet) are the strongest. Our eyes more easily perceive blue than purple.
Therefore, by process of elimination of all the other colors, the sky is blue!
At home experiment:
Get a glass of water, add soap to it to make the water cloudy.
Then shine a white light flashlight through the water.
Your eyes will see blue water!