Frank, Mark G., and Gilovich, Thomas, "The Dark Side of Self- and Social Perception: Black Uniforms and Aggression in Professional Sports", Journal of Personality and Social Psychology, 1988, 54:1:74-85

The authors found that wearing black uniforms in profession sports led to increased aggression and more penalties. Movement from a non-black to a black uniform team resulted in an increase in penalties. Laboratory studies where teams wore black and non-black uniforms showed increases in both the perceptions of referees and the actions of the players themselves.

Black is a universally "bad" color, with connotations of agression and death.

They analyzed five NFL teams with 50% or more black in their uniforms. And five NHL teams. According to impartial observers of the uniforms, they looked more malevolent. After analysis of agression penalities, all of the dark color teams were near the top of the group in agression scores. Two hockey teams that switched to black uniforms during the season saw an increase in penalities.

Then they had subjects review a staged football game between black and non-black uniforms (two identically staged games with the uniforms reversed in the two versions). The results showed that the subjects felt that the black uniform team was more likely to be penalized. Turning off the color on the video eliminated the effect.

Another lab test showed that donning black uniforms also changed the agressiveness intent of college students involved in competitive games. Wearing black uniforms caused them to choose more aggressive games from a list for further compeition.