This thesis employs a close reading of archival and published sources to explore the origins of colour vision science in 19th century Britain. By drawing attention to wide ranging dialogues and disagreements between diverse figures with different visions of colour, including physicists David Brewster, James Clerk Maxwell, and Lord Rayleigh, politician and philologist William Gladstone, ophthalmologists Frederick Edridge-Green and Robert Carter, and anthropologist W.H.R Rivers, I show that 19th century colour vision science was not narrowly confined to the quantification, measurement, and classification of colours. It was instead shaped by deeper metaphysical questions and wider political concerns. These questions and concerns included the implications of natural law, free-will, and materialism for scientific understandings of reality, the limits of Darwinian understandings of humanity, the legitimacy of scientific experts and institutions in determining public policy, and the history, future, and advancement of civilization.

I argue that the widespread use of spinning discs as an experimental research technology, promoted by Brewster and Maxwell, combined with the mainstream acceptance of Maxwell’s theoretical model of ‘coterminal response curves’, generated conflicts between competing understandings of perception, vision, and colour in the second half of the 19th century. These conflicts stemmed from the establishment of new conventions, inspired by Maxwell’s work, which held that scientists should maintain a practical and analytical distance from their own visual experiences, that the visual experiences of test subjects should be treated as untrustworthy phenomena in need of further analysis, and that the meaning of subjective experiences are contained within, and revealed by, mathematical models that accord with a rational understanding of the physical world. These practical and metaphysical approaches to the meaning of human experience did not end with the conflicts they generated in the second half of the 19th century but continue to bear on broader contemporary understandings of truth and illusion in scientific practice and popular imagination.