In fact, we see only a small portion of all of the electromagnetic energy that exists. X-rays, radar and radio waves are also types of electromagnetic energy, but our eyes are not sensitive to any of those types. White looks white, because it absorbs no colours, and reflects all colours. Black looks black, because it absorbs all colours, and reflects none. Green looks green, because it absorbs all colours but green, which it reflects.
Colour blindness is the inability to distinguish colours.
The most common colour blindness is red-green, which means that people have difficulty distinguishing red and green things, especially at weak saturations. Other colours are combinations of those colours. Colour blindness results from a lack of one or two of the receptors. Overuse, from fatigue or overstimulation, of one component will lead to the use of its complement, or opponent. Present thinking holds that both of these theories are correct, but they refer to different stages of colour processing.