From cars to furniture to iPods, we make decisions about colour all the time. Now, scientists are starting to figure out why we like the hues we do.
According to a new study, it is our experiences that determine which colours we prefer. It is the first to experimentally test the long-suspected idea that people like the colours of the things they like.
The findings may help explain why blue is pleasing to people everywhere, why Japanese women tend to like light colours, and why dark yellow is generally unappealing, among other trends.
On the flip side, the study also hints at why one woman might buy orange socks, while the next shopper picks brown - in turn, offering tantalising fodder for designers, artists and marketing experts.
"I might like purple more than you because my sister's bedroom was purple and I had positive experiences there," says Karen Schloss, a graduate student in psychology at the University of California, Berkeley. "Your own personal preference is determined by all the entities you've encountered of that colour and how much you liked them."
In their attempts to understand why people like certain colours, scientists have focused on evolution. The main theory is that we like colours that are tied to things that are healthy and promote survival.
A blue sky, for example, indicates calm weather, which might explain why blue tends to be a favoured colour across cultures. Dark yellows and oranges, on the other hand, invoke urine, faeces, vomit and rotting food. As expected, there is usually a dip in preference for these hues in studies around the world.
Scientists have also predicted, with mixed results, a preference for red among women, who would've needed to spot red berries against green foliage in our ancestral hunter-gatherer societies.
Despite those general trends, there are wide-ranging differences among individuals about which colours they like. Schloss and colleague Stephen Palmer wanted to know why.
As part of a series of experiments, the researchers showed slide shows of coloured objects to a group of participants. The images were biased, so that some people might see nice red things, like yummy strawberries, but unpleasant green images like slime. Others saw unpleasant red things like blood but nice green objects, like trees.
Afterwards, the researchers reported in the Proceedings of the National Academy of Sciences, people preferred whichever colour had been linked to the positive images they saw, whether red or green.
In another preliminary study, the researchers found that Berkeley students who ranked highest in school spirit had the strongest preferences for blue and gold, their school's colours, and the most distaste for red and white, the colours of their rival Stanford.
Spirited Stanford students showed the opposite pattern, suggesting that social affiliations can influence which colours we like at different times in our lives.
"Their study is a really neat experiment to prove something that we have suspected for a long time," says Yazhu Ling, a vision scientist at the University of East Anglia in the United Kingdom. She and colleagues established a theory that our systems for ranking colours are hardwired, even if our actual colour preferences are malleable.
"You see loads of articles online about what colour you like and what that says about what kind of person you are," she says. "There is not actually scientific support for that. But it shows that people are generally interested in the subtle differences between people and what has driven that. Colour provides a tool to understand why we like some things more than others."