By Paul Rincon
BBC News science reporter
Wearing red can give competitors in sporting contests the winning edge, British scientists have claimed.
Red may be an ancient signal of dominance
A report in Nature by Durham University academics suggests donning red kit increases the probability of winning physical contests in a range of sports.
The researchers claim the effect could be down to a deep-seated evolutionary response that works subconsciously to put opponents on the back foot.
More thought may need to be given to the colour of sportswear, they say.
Previous research by different scientists showed levels of the male sex hormone testosterone are highest in footballers when they play a game at home.
Co-author Dr Robert Barton said such a response might be acting here.
"Whether red suppresses the testosterone of the opponent or boosts the testosterone of the individual wearing red, we don't know at the moment. We're going to look at that," Dr Barton told the BBC News website.
"My hunch is that there is a bit of both going on."
Tipping the balance
Barton and colleague Russell Hill studied four combat sports during the 2004 Athens Olympic Games: boxing, tae kwon do, Greco-Roman wrestling and freestyle wrestling, where contestants were randomly assigned either red or blue colours.
They found that, across the four disciplines, contestants wearing red won significantly more fights.
This does not discount the importance of factors such as skill and strength, stress the researchers.
A deeper analysis of the data showed the colour advantage tipped the balance only when competitors were relatively evenly matched.
The influence of colour on such contests may have its roots in our evolutionary past. In the animal world, red is thought to be related to fitness, aggression and high levels of testosterone.
Male mandrills, for example, have red colouration on their faces, rumps and genitalia that they use to communicate their fighting ability to other males.
Dr John Lazarus, a biologist at the University of Newcastle, said he was intrigued by the finding but not convinced red held particular significance over other colours as a dominance signal.
"To take another monkey species, vervet monkeys have blue testicles and the ones with the bluer testicles are more dominant," Dr Lazarus told the BBC News website.
Come on you reds
The Durham researchers also carried out a preliminary analysis of results from the Euro 2004 soccer tournament showing that five squads had better results when playing in red.
The three teams that have dominated English football over the past 50 years - Liverpool, Manchester United and Arsenal - sport red liveries.
Other factors, such as money, clearly have a strong influence on a club's ability to take home trophies.
But, says Dr Barton, "as a Chelsea supporter, I would say that once you control statistically for the unfair advantage of colour, we actually won the championship last year."
The Durham scientist suggested the findings could have implications for regulations on sportswear in competitions.
"We wouldn't go so far to suggest what they should do. But something that's possibly interesting is that in many British sports there used to be the regulation that competitors had to wear white," he said.
"I just wonder whether that was a subconscious awareness of the need to establish a level playing field."