" It was Vivi who’d worked out the code that the triangles represented, through talking to the other women in the barracks. Yellow ones were worn by Jews, and sometimes a red inverted triangle was overlain by a yellow one the opposite way up, indicating a dual categorisation. Green triangles were worn by convicted criminals, who were often put in charge of work parties as they were prison-toughened which made them ruthless overseers, or kapos as they were known in the camp, prepared to mete out punishments to their fellow inmates. Black was for those classed as mentally "

― Fiona Valpy , The Dressmaker's Gift