A long time ago, the sky was only gray and no other color. Always gray. Never changes. Not even a hint of blue.
One day, the famous artist, Claude Monet, decided to have a walk on the path from his home. Now, he finally noticed how sad the sky looked with the dull, gray color. So Claude Monet decided to paint it blue with his magic paintbrush.
When he was done, the sky totally changed, now looking natural and happy. Claude Monet grinned from ear to ear.
Even thought now, sometimes our sky can be gray or some other colors, that is when parts of the sky wants to be back in their gray form. But mostly, our sky is blue.
This is why, now, our sky is blue.