When did humans first see colour? Trichromacy seems to have been around for at least 30 million years. Our very early ancestors, however, were probably nocturnal and had uv vision. It is thought that about 80 million years ago we developed sensitivity at the longer wavelengths, became dichromats and eventually trichromats. We now know that some humans in fact are tetrachromatic and have four cones. 

The Over The Rainbow team also discuss the arguments about whether light is actually coloured or whether it just looks coloured. Linguistic relativity and the colour vision of the Himba tribe (Namibia) are also mentioned.