In particular the color red has been found to influence sports performance. During the 2004 Summer Olympics the competitors in boxing, taekwondo, freestyle wrestling, and Greco-Roman wrestling were randomly given blue or red uniforms. A later study found that those wearing red won 55% of all the bouts which was a statistically significant increase over the expected 50%. The colors affected bouts where the competitors were closely matched in ability, where those wearing red won 60% of the bouts, but not bouts between more unevenly matched competitors. In England, since WWII, teams wearing red uniforms have averaged higher league positions and have had more league winners than teams using other colors. In cities with more than one team, the teams wearing red outperformed the teams wearing other colors. A study of the UEFA Euro 2004 found similar results. Another study found that those taking penalty kicksperformed worst when the goalkeeper had a red uniform. More anecdotal is the historical dominance of the domestic honors by red-wearing teams such AFC Ajax, FC Bayern Munich, Liverpool F.C., and Manchester United F.C.. Videos of taekwondo bouts were manipulated in one study so that the red and blue colors of the protective gears were reversed. Both the original and the manipulated videos were shown to referees. The competitors wearing red were given higher scores despite the videos otherwise being identical. A study on experienced players of first-person shooters found that those assigned to wear red instead of blue won 55% of the matches.
There are several different explanations for this effect. Red is used in stop signs and traffic lights which may associate the color with halting. Red is also perceived as a strong and active color which may influence both the person wearing it and others. An evolutionary psychology explanation is that red may signal health as opposed to anemic paleness, or indicate anger due to flushing instead of paleness due to fear. It has been argued that detecting flushing may have influenced the development of primate trichromate vision. Primate studies have found that some species evaluate rivals and possible mates depending on red color characteristics. Facial redness is associated with testosterone levels in humans, and male skin tends to be redder than female skin.