We had a lot of fun with our third colour podcast. We started off talking about the colour vision of unicorns and my co-presenter Huw put forward a very entertaining suggestion of what their colour vision would be like if they existed. We then explored the effect of colour and light on health. The effect of colour on heart rate and blood pressure is still contentious which is extraordinary, I think after all of these years that the scientific community has been studying colour. We also spoke about the role of colour and light on sleep. Sleep is really really important. Watching this TED talk by Matthew Walker about sleep might be the most important thing that you watch this year.