To identify prisoners in the camps according to their "offense", they were required to wear colored triangles on their clothing. Although the colors used differed from camp to camp, the colors most commonly were:
Yellow: Jews -- two overlaid to form a Star of David, with the word "Jude" (Jew) inscribed; mischlings, i.e., those who were deemed to be only part Jewish, often wore a single yellow triangle
Red: Political dissidents, including Communists
Green: Common criminals. Criminals of Aryan descent were frequently given special privileges at the camps, and power over other prisoners.
Purple: Religious fundamentalists (defined as persons belonging to Christian sects whose teachings forbid fighting in wars), most notably Jehovah's Witnesses
Blue: Immigrants.
Brown: Roma and Sinti (Gypsies)
Black: Lesbians and "anti-socials" (alcoholics and the "work-shy")
Pink: Gay men