The Mackenzie Memorial Lecture, 1977. Of divers colours

I shall discuss the nature of the sensation of colour and the reason for our colour vision, leading on to the existence of defects in that sense. I will consider the different kinds of such defects and the arguments for the use of particular tests in varying circumstances. I report the result of a recent survey of the value of a careers advisory service for "colour blind" school children seen between 1965 and 1977 (primarily red-green blind). This leads to examples of the value of these tests in genetics, and in the early diagnosis of disease or toxicity. I shall also describe the various modifications I have made to the 100-hue test, with its eventual automation both for computation and recording. Finally, the recommendations I make for future progress cover routine examination, both on starting primary education and on entering secondary education, analysis of the colour task at work, and the adoption of an enlightened system of colour coding.