I really like the color blue. Do you like blue? It's one of three primary colors. 
Yeah, I like blue, do you know why the sky is blue ?
The sky is blue because it's the most widely scattered wavelength coming through our atmosphere.
That is interesting, is it the same reason why we see water as blue ?
It's called Rayleigh scattering, and it can happen in transparent solids (like prisms) and liquids, but is most often seen in gasses. 
Oh, and do you know why blue is a primary color, why not purple ?
The primary colors are based on the RGB color model, which is an additive color model. Red, green, and blue light are added together in various ways to create many different colors. Purple is a result of this additive process.
OK, so blue cannot be produced by adding color, but green can produced by adding yellow to blue, so why green is used in the RGB model ?