Do you know any Scientific REASON for light blue color of the SKY ??  

That's not a silly question. :-) Thomas Edison asked questions, and he made the lightbulb. Anyway, after searching around, I think that what you have in your question is correct. Believe it or not, there are gasses in our atmosphere. He dispersenet of light through those gasses, and our eyes makes the sky blue.

Not much knowledge in science, but as I have ready, it's due to scattering of sun rays due to dust particles, present in atmosphere, that makes the sky look ble otherwise there is no color. since sky is not like a plate or surface it's just space.

Right as your are, there is nothing silly or funny to be there is a reason in everything, it simply cant exist out of somewhere, there is always a scientific explanation for everything some are a mystery and some may not, some great people like Thomas Edison we use light as it is now, sky simply cant change color it depends on which color that falls on object that gets reflected that again reflected light reaches our eye.as we see everything we see is composed of light rays that show the path or even simply help us identify objets.

When i was in school i read in social study book that water is the reason of sky.