Opsins are the photosensitive proteins in the eye, responsible for converting a photons of light into an electro-chemical signals. Different opsins react to different wavelengths of light, each corresponding to a different band of colour. In humans, the 'visible spectrum' of light (a very anthropocentric term) is covered by three opsins, receptive to red, green and blue wavelengths. Other animals have opsins that are capable of subdividing the 'visible spectrum' and responding to a large number of very specific wavelengths of interest. All in all, the ability to detect light and recognise colour is not the same throughout the animal kingdom. In this episode, we are joined by Dr James Fleming of Keio University, Japan to discuss the evolution of opsins in the ecdysozoa (the group containing arthropods and a fair few worms). We talk about the fundamentals of light detection and how, using phylogenetics, we are able to tell which colours certain extinct animals were capable of detecting.