Anya Hurlbert is one of the most respected researchers into the way we see colour. When, a few years ago, an online image of a blue and black striped dress spun virally out of control, it divided us all. Half of us were adamant the dress was white and gold, and the other half convinced it was blue and black. Colour is, Anya argues, made in the mind, not just out there in the world and we don’t always see it in the same way.