The system of badges varied between the camps, and in the later stages of the war, the use of badges dwindled in some camps, and became increasingly accidental in others. The following description is based on the badge coding system used before and during the early stages of the war in the Dachau concentration camp, which had one of the more elaborate coding systems.
Shape was chosen by analogy with the common triangular road hazard signs in Germany that denote warnings to motorists. Here, a triangle is called inverted because its base is up while one of its angles points down.
 Single trianglesRed triangle—political prisoners: liberals, communists, trade unionists, royalists, social democrats and socialists, Freemasons, anarchists.
Green triangle— "professional criminals" (convicts, ofttimes Kapos, serving in exchange for reduced sentences or parole).
Blue triangle—foreign forced laborers, emigrants.
Pink triangle—sexual offenders, mostly homosexual men but rarely rapists, zoophiles and paedophiles.
Purple triangle— Bible Students, a term taken from a name of, and primarily referring to, Jehovah's Witnesses, though a very small number of pacifists and members of other religious organizations were also imprisoned under this classification
Black triangle—people who were deemed "asocial elements" and "work shy" including
Roma (Gypsies), who were later assigned a brown triangle
The mentally ill
Vagrants and beggars
Brown triangle—Roma (Gypsies) (previously wore the black triangle).
Uninverted red triangle—an enemy POW, spy or a deserter.
People who wore the green and pink triangles were convicted in criminal courts and may have been transferred to the criminal prison systems after the camps were liberated.Double-triangle badges resembled two superimposed triangles forming a Star of David, a Jewish symbol.
Two superimposed yellow triangles, the "Yellow badge"—a Jew
Red inverted triangle superimposed upon a yellow one—a Jewish political prisoner
Green inverted triangle upon a yellow one—a Jewish "habitual criminal"
Purple inverted triangle superimposed upon a yellow one—a Jehovah's Witness of Jewish descent
Pink inverted triangle superimposed upon a yellow one—a Jewish "sexual offender"
Black inverted triangle superimposed upon a yellow one—"asocial" and "work shy" Jews
Voided black inverted triangle superimposed over a yellow triangle—a Jew convicted of miscegenation and labeled as a "race defiler"
Yellow inverted triangle superimposed over a black triangle—an Aryan (woman) convicted of miscegenation and labeled as a "race defiler"
Like those who wore pink and green triangles, people in the bottom two categories would have been convicted in criminal courts.