my son's questiom

The leaves of the trees are green because of the presence of the pigment called chloroplasts. Sky appears blue because it scatter blue light of the 'vibgyor' more than other colors. Water is transparent because it has low refractive index.

Here is an idea, have your son to make a painting any painting that it be from his imagination it is important that you let him draw things that are not real or things that don't have a particular color like for example a gift box a gift box can have any color it can be blue or green or yellow unlike things like the sky it is always blue! after he finishes the painting ''lets say he draws a yellow gift box for example'' ask him why the box is yellow! no matter what his reasons are try to make him connect them to the same reasons behind the colors of the sky and tree! children don't need logic and reason as much as they need imagination so don't ruin it for them with scientific complications if u give him the scientific explaination it will be like when a child asks who created us and u reply god! then the child asks another question to which im sure you have no logical or scientific explaination, who created god? how do u know know if god exists if you never saw god? children are happy creatures because they have a world of their own made up of their imagination why should we be in a hurry to ruin it for them?! just let them enjoy it! it also helps them practice thinking! don't make it easy for them to find answers let them imagine and think let them find their own reason. my father sometimes refused to answer my questions u know what i did later when i grew older? i read books and paid more attention to the world around me in order to find my answers. Someone painted the sky in blue for the same reason ur son will paint a box in yellow and that's about it!

Well simply tell him that this is the nature of life and you can't define it simply yea .

leaves are green due to chlorophyll.

Maybe you can say that is a natural phenomenon.

I believe the green in plants and trees is because of the chlorophyll they contain within the leaves. I hope that helps a little. xxx

This is one of those to get them to hush kind of answers and is kind of religious but they way I handled the situation was by telling my son that when god created the wrold it was like a paint by numbers and he needed to only match the numbers with the coressiponding colors. I might not be the best answer but it did the job and my son grew up and later found out the whole scientific process of color and such so it all work out eventually.

the green in plants has something to do with photosynthesis, the sky is blue because of the reflection of the water and well i honestly don't know why water is transparent :P

I'm guessing your son is not very old and still goes to school... If I were you I would tell him "what do you think??" then just agree with what he says... :)