For a stable visual world, the colours of objects should appear the same under different lights. This property of colour constancy has been assumed to be fundamental to vision, and many experimental attempts have been made to quantify it. I contend here, however, that the usual methods of measurement are either too coarse or concentrate not on colour constancy itself, but on other, complementary aspects of scene perception. Whether colour constancy exists other than in nominal terms remains unclear.

There are serious reasons for accepting each of these propositions individually but there are apparently insurmountable difficulties with accepting all three of them simultaneously if we assume that color is a single property. 1) and 2) together seem to imply that there is some property which all organisms with color vision can see and 3) seems to imply that there can be no such property. If these implications really are valid then one or more of these propositions will have to (...) be rejected in spite of whatever reasons can be given for their apparent acceptability. Before going on to discuss possible resolutions of this apparent contradiction it is worth pointing out there our three propositions are not all of a kind. Proposition 1) is a metaphysical thesis about the ontological status of color and proposition 3) is an empirical thesis about what properties organisms with color vision are capable of detecting. If you accept 1) then 2) will appear to verge on the trivial, but if 1) is denied then the status of 2) will appear more problematic. In what follows I will have more to say about why we either should or should not accept all three of these propositions. (shrink)

In this target article the following hypotheses are discussed: (1) Colour is autonomous: a perceptuolinguistic and behavioural universal. (2) It is completely described by three independent attributes: hue, brightness, and saturation: (3) Phenomenologically and psychophysically there are four unique hues: red, green, blue, and yellow; (4) The unique hues are underpinned by two opponent psychophysical and/or neuronal channels: red/green, blue/yellow. The relevant literature is reviewed. We conclude: (i) Psychophysics and neurophysiology fail to set nontrivial constraints on colour categorization. (ii) Linguistic (...) evidence provides no grounds for the universality of basic colour categories. (iii) Neither the opponent hues red/green, blue/yellow nor hue, brightness, and saturation are intrinsic to a universal concept of colour. (iv) Colour is not autonomous. (shrink)