For the subject of vision, there is no single equation or view that explains everything. Each problem has to be addressed from several points of view.
(David Marr 1982:5)
Philosophical issues about colour must be addressed in relation to issues about levels of explanation for vision. This chapter will demonstrate this point by considering recent physiological, psychophysical, and computational theories of colour vision.
It has now been more than three decades since Leo M. Hurvich and Dorothea Jameson proposed a quantitative, psychophysical formulation of the opponent process theory of colour vision (Hurvich and Jameson 1957), and Gunnar Svaetichin and Edward F. MacNichol Jr discovered wave-length-dependent opponent responses in the horizontal cells of fish retinas (Svaetichin and MacNichol 1958). In comparison, the computational study of colour vision is quite young: Edwin Land's 'retinex theory' (Land and McCann 1971; Land 1977) was until recently the only computational model available. Despite its youth, however, computational colour vision has now become a distinct area of research in visual science, one which also has a share in the larger cooperative research programme known as cognitive science. The results and prospects of this new interdisciplinary style of research on colour vision provide one of the topics of this chapter.