We can never know what was going through our ancestors’ minds, tens of thousands of years ago, when they first picked up natural crayons and began painting their bodies. But it is perhaps significant that they chose a rich, red ochre – the colour of our blood and a vivid reminder of life, and death.

Today, shades of scarlet are linked with power, aggression, and sex – from the vermilion of the British Queen’s royal regalia to the gaudy neon of Amsterdam’s red–light district. And those associations may not be coincidence. A new branch of science called “colour psychology” has found that red can have a profound influence on our mood, perceptions and actions. Wearing red can even change your physiology and balance of hormones and alter your performance in a football match. So what is it about the shades of ruby, crimson, and scarlet that makes them so potent?

Warning sign

There is no doubt that our perception of red coincides with one of the most important events in our evolutionary history. Many mammals, like dogs, fail to differentiate between red and green. But as our early primate ancestors were adapting to life in the jungle, they evolved a new kind of cell in their retina that allowed them to pick out the bright, red fruit from the foliage. That enhanced perception would then lend itself to new forms of social signalling. Red skin – caused by blood pumping near the surface of the skin – is an important sign of dominance for many primates. Mandrill monkeys are perhaps the most famous example, with vivid markings on their face and bottom that signal their position in the group’s strict hierarchy; the fitter, and more dominant an individual is, the redder he appears. Reading their competitors’ fitness therefore prevents the lower ranking monkeys to take on a fight they are sure to lose.