This review is an enquiry into why the early clinical evidence for a colour centre in the cerebral cortex of man was so successfully dismissed for the best part of a century. The imperfection of this evidence cannot be the reason, for the same evidence that was rejected earlier is accepted today. Instead, it was because the prevalent concepts of vision as a function, and of the role of the cerebral cortex in it, dominated facts and prevented acceptance of evidence showing a specialization for colour in the visual cortex. It was only after those concepts were overthrown by the demonstration of functional specialization in the visual cortex of the primate that the evidence for a colour centre in the human brain became acceptable. Today, our new knowledge of the colour areas and pathways in the primate brain allows us to give a more complete account of the pathophysiology of cerebral achromatopsia in man.