Butterfly pea flower tea (https://en.wikipedia.org/wiki/Butterfly_pea_flower_tea), commonly known as blue tea, is a caffeine-free herbal tea, made from a infusion of the flower petals or whole flower of the Clitoria ternatea plant. The color comes from Delphinidin (https://en.wikipedia.org/wiki/Delphinidin), a pH-sensitive plant pigment, which changes its color from blue to purple when lemon juice (an acid) is added. The taste is earthly and light. Makes also fun drinks for kids.