http://www.policeone.com/police-products/apparel/undergear/articles/99417-The-psychological-influence-of-the-police-uniform/ wrote:
<<The police uniform is a tradition as old as the field of law enforcement itself In 1829 the first modem police force, the London Metropolitan Police, developed the first standard police apparel. These first police officers, the famous "Bobbies" of London, were issued a dark blue, paramilitary-style uniform.. The color blue was chosen to distinguish the police from the British military who wore red and white uniforms at the time. The first official police force in the United States was established in the city of New York in 1845. Based on the London police, the New York City Police Department adopted the dark blue uniform in 1853, Other cities, such as Philadelphia, Boston, Cincinnati, Cleveland, Buffalo, and Detroit quickly followed suit by establishing police departments based on the London model, including the adoption of the dark blue, paramilitary-style uniform.
To this day, the majority of police uniforms in. the United States continue to have a paramilitary appearance and are generally of a dark color. Darker colors may have been preferred for their case in cleaning and their ability to help conceal the wearer in tactical situations. Dark colors help cover up stains and keep the officer from being easily spotted by lawbreakers, especially at night.
The Influences of Color
The majority of police uniforms in the United States today are produced in darker colors such as black, blue, brown, green, and grey. Just as with the style of the police uniform, the color of the police uniform has meaning. Psychological tests have found that people associate colors with specific moods. For example, red is generally associated with excitement and stimulation, thus explaining why it is often a color in flashing emergency vehicle lights. These tests have also found that the color blue is associated with feelings of security and comfort, and black is most often associated with power and strength. Studies of both high school and college students in the United States have found that students perceived light colors such as white and yellow as weak, but also good and active, The same students perceived dark colors such as black and brown as strong and passive, but also as bad. These results were not based on cultural influences because they did not vary with the race of the students.
Even people in Europe, Western Asia, Central Africa, and the Middle East had similar perceptions of colors. Across all cultures that have been studied, light colors are consistently associated with goodness and weakness, while dark colors are consistently perceived as strong but evil. On psychological inventories, test subjects rate lighter colors as more pleasant and less dominant. Dark colors on the other hand elicit emotions of anger, hostility, dominance, and aggression.>>