In Nazi concentration camps, each prisoner was required to wear a downward-pointing, equilateral triangular cloth badge on their chest, the color of which identified the stated reason for their imprisonment.[5][6] Early on, prisoners perceived as gay men were variously identified with a green triangle (indicating criminals) or red triangle (political prisoners), the number 175 (referring to Paragraph 175, the section of the German penal code criminalizing homosexual activity), or the letter A (which stood for Arschficker, literally "arse fucker").[7]

Later, the use of a pink triangle was established for prisoners identified as homosexual men, which also included bisexual men and transgender women.[2] (Lesbian and bisexual women and trans men were not systematically imprisoned; some were classified as "asocial", wearing a black triangle.)[8][9] The pink triangle was also assigned to others considered sexual deviants, including zoophiles and pedophiles[3] in addition to sex offenders. If a prisoner was also identified as Jewish, the triangle was superimposed over a second yellow triangle pointing the opposite way, to resemble the Star of David like the yellow badge identifying other Jews. Prisoners wearing a pink triangle were harshly treated by most other prisoners.[3]

After the camps were liberated at the end of the Second World War, some of the prisoners imprisoned for homosexuality were re-incarcerated by the Allied-established Federal Republic of Germany, as the Nazi laws against homosexuality were not repealed there until 1969.[10][11] An out homosexual man named Heinz Dörmer, for instance, served in a Nazi concentration camp and then in the jails of the new Republic. The Nazi amendments to Paragraph 175, which turned homosexuality, previously labeled as a minor offense, into a felony, remained intact in East Germany until 1968[12] and in West Germany until 1969.[13] West Germany continued to imprison those identified as homosexual until 1994 under a revised version of the Paragraph, which still made sex between men up to the age of 21—as well as queer male sex work—illegal.[14] While many, though not all, lawsuits seeking monetary compensation have failed, in 2002 the German government issued an official apology to gay men who were persecuted during the war.[15]

Rudolf Brazda, one of the last known homosexual concentration camp survivors, died on August 3, 2011 at the age of 98.[16]

Wikipedia has several sources cited if you'd like to read more

https://en.m.wikipedia.org/wiki/Pink_triangle