The color of the light coming from the sun is white (the sun appears to be yellow, but if you look at it from the space or the moon it's white), when sunlight enter the atmosphere some of the light waves (including blue light) are absorbed by the gas molecules in the atmosphere and then radiated in different directions, that's why the sky is blue whichever direction you look in the sky.

The sky is blue because of the water vapor

you sure must have missed 6th grade science class a lot.