Colours in ordinary life interact in complex ways with light, unlike the colours represented by colour solids or the "reduced" colours sometimes considered by psychologists. Wittgenstein's explorations of colours in ordinary life and light are intended to illustrate his view that the world of colours is very complex and displays no system or at least no system rooted in the natures of colours. I look at the relations between what Wittgenstein says about colours and what two great psychologists, David Katz and Karl Bühler, had to say about colours and light. The two psychologists win.