Unsurprisingly philosophers have had a lot to say about colour. Largely this is because it is ubiquitous and provides us with a handy way of identifying and describing objects. But it also interests because it springs surprises. We are intrigued, most of us anyway, by the way paints mix and lights combine, the effect of surroundings on how colours are perceived, the ability of some people to discriminate between colours the rest of us take to be the same, the prevalence of colour blindness, the fact that colours are sometimes perceived along with sounds, the existence of languages with less –or more or different –words for colours than in English and so on. What causes philosophers to reflect on colour, however, is typically different. They are inclined to focus on the sort of thing colour is, what we can know about the colours of surfaces and objects, the place of colour in the world, how we come, if at all, to know the true colours of objects, whether everyone sees the same colours and a host of similarly troublesome questions. Unlike questions about colour mixing, colour perception and the like, questions answerable by empirical investigation, the philosopher's questions defy easy answers and, as such, serve as prime material for speculation and debate.

Though best known for his discussion of language, the mind and mathematics, Ludwig Wittgenstein (1889–1951) was also uncommonly exercised by problems posed by colour during the years he was seriously engaged in philosophy (roughly 1911–19 and 1929–51). He took colour to be ‘a stimulus to philosophizing [regen Philosophieren an]’ (Culture and Value, p. 76, dated 11 January 1948) and was stimulated to write about it. Indeed, he discussed it more searchingly than other major philosophers. He touched on colour in his earliest writings, Notebooks 1914–1916 and Tractatus Logico-Philosophicus (1918/22), treated it more fully in the so-called transitional writings, notably Philosophical Remarks (1931) and The Big Typescript (1933/37) and examined it at length in Remarks on Colour (Bemerkungen über die Farben) (1950/77), a collection of practically all the remarks on the topic he composed during last year and a half of his life. In this late work, colour is front and centre, not as it mostly is in previous works, introduced to illustrate a point.