I often think about this. We just covered the eye in biology and learned that all human eyes see the same colours, unless you are colourblind. My teacher said all people have the same rods and cones in their eyes unless they are colourblind.

If you were born colourblind you would grow up seeing the alternate colours and learn them. I think it is quite possible that alot of people are colourblind and don't realise since they don't know any other.