Colours

From an early age we are taught numbers, letters, colours, behaviours etc. A conversation with friends the other day about colour blindness made me wonder about colours and the fact that we've been taught that red is red and blue is blue. Of course that got me wondering that what if we'd been taught that red was blue and blue was yellow? What's to say that we've been taught is correct, and that those that are colour blind are actually seeing things correctly!