Okay kiddo, have you ever looked up at the sky and noticed that it's sometimes very bright and blue? That's what we call a blue sky. And have you ever seen the sun shining in the sky and noticed that it's very bright and kind of looks like a circle? That's the sun!
Now, do you know what makes the sky blue? It's actually all because of something called the atmosphere. The atmosphere is like a big blanket of air that surrounds the Earth.
When the sun shines down on the Earth, it sends out all sorts of colors in the form of light. But the atmosphere gets in the way and scatters all of those colors around.
Now, here's the really cool part: the blue color in the sky is actually the light scattering more than some of the other colors. So when you look up, you see a lot of blue light scattered around in the atmosphere, which makes the whole sky look blue!
And as for the sun, it looks white because it's actually made up of all the colors of the rainbow, mixed together. But when you look directly at the sun, it can hurt your eyes, so it's really important to never look directly at it.
So that's why we have a blue sky with a white sun!