Blue butterfly pea (Clitoria ternatea) is a herbaceous climbing plant of the Fabaceae family. It is native to East Asia but is said to have originated from Latin America. Its pea-shaped flower contains proanthocyanidin, a polyphenol that gives the flower its characteristic blue color. Butterfly pea is a versatile natural pigment; its color depends on the pH level of a solution. It has a blue hue in neutral environments, purple (and even red) in acidic environments, and green in alkaline environments.
 
Usage:
Butterfly pea is soluble in water.
Its pigment effects are pH-dependent:
Blue in neutral environments.
Purple in acidic environments.
Green in alkaline environments.