The violet shades of synthetic red and violet dyes composed of linear quinacridones that are made from terephthalic acid. Quinacridone dyes can exist in four crystalline allotropes, two of which are sold as red and violet pigments. Although synthesized in 1896, quinacridone colors were first recognized as useful pigments and marketed by DuPont in the 1950s under the name Monastral. They are lightfast colorants used in paints, printing inks, and plastics.一種由合成紅和紫染料形成的紫色色澤，是由對苯二甲酸製成的線性喹吖酮形成。喹吖酮染料可以四種同素異晶體存在，其中兩種做為紅色及紫色顏料販售。喹吖酮顏料早在西元1896年即成功合成，但在1950年代才被視為可用顏料，由杜邦公司（DuPont）以「單星（Monastral）」為顏料名牌名稱上市販售。喹吖酮顏料為耐光著色劑，用於油漆、印墨及塑膠。