Butterfly pea flowers (Clitoria ternatea - aka blue pea, Asian pigeonwings) are unique blue-purple flowers originally from Southeast Asia. What makes them special is their ability to color liquids. Steep some of them in just-boiled water, and they’ll quickly turn it a striking blue color.
Even more exciting, if you add an acidic ingredient (like lemon or lime juice, vinegar, etc), that color will quickly shift to a gorgeous purple.
Butterfly pea flowers are traditionally used to make tea (together with other ingredients, like spices), and impart a very mild vegetal flavor. The colored water can also be used to cook rice to impart color, or can be frozen into ice cubes.
Both traditional Ayurvedic medicine and traditional Chinese medicine have attributed health benefits to this flower.