ABSTRACT
For philosophers of perception and knowledge, colour illusions are somewhat ho-hum examples of a more general phenomenon. Such philosophers are concerned with illusions, but not with colour illusions, per se. Such a phenomenon is interesting for scientists, especially to the extent that the phenomenon is not fully understood, but their interest does not concern its being an illusion, if indeed it is one. Scientists are interested in colour experiences, understood very broadly, and so in colour illusions, but not with colour illusions, per se. That many philosophers have thought that illusions tell us something about the nature of colours is one reason, perhaps the principle reason that philosophers have been concerned with colour illusions. The special interest that philosophers have in colour illusion, then, goes hand in hand with worries about the nature of colours, and so debates about whether colours are objective or subjective, primary or secondary, relative or non-relative.
