This paper has two distinct purposes. One of them is to make explicit some of the themes that the other essays on colour in this book have in common. And the other purpose is to make a contribution to one of those themes. Very briefly and generally, these themes are the ways colours look different to different people, and the ways in which painting and other visual arts can exploit these differences. The papers in this book by John Clark, Bernard Harrison, John Gage, Peter Lloyd-Jones, and Michael Podro connect with each other in many ways, some of which can be described in terms of questions about individual variation in colour perception. These are the connections that I hope to make explicit. In doing this I will have to straighten out some differences between the ways these writers use their terms and some apparent differences in their aims. The easiest way to do this is to develop an idea of my own. That idea is, just as briefly, that some differences between different people's perception of colour can be represented by taking people to have differing perspectives on the colour solid which is common to us all. And that one way in which paintings and the like are expressive is by imposing on the viewer's attitude to colour a different such perspective. (I described the colour solid below, and explain these perspectives via a technical notion of a colour transform.)