explain how a computer screen and the eye interact to produce the variety of colors that we see from the 3 colors that are actually displayed on the screen?

Each pixel of light coming from your computer is made up of a combination of Red, Blue and Green light of different intensities. As this pixel of light is so small your eye only "sees" the combination of those 3 pixels as the intended colour. (as opposed to just red, green and blue light) (This is also known as additive colour mixing)