I wasn't going to join this but you guys peaked my interest. I did some digging and the answer is. It depends on your point of reference for what a colour is.
Do you consider what you perceive with your eyes to be the colour spectrum, then yes white and black can be considered as colours.
However if you consider what is actually emitted by electromagetic waves and how your eyes detect the colour white (red, green and blue colour cones are stimulated by their respective electromagnetic waves, like how we are all stimulated by this discussion ) then no neither black or white is a colour.
I, like most humans perceive with my eyes.