When I made Nyonya dumplings not long ago, many friends asked me about the blue coloring I used to dye the rice. It is from blue pea flower/butterfly pea flower, it is a natural food coloring with a lot of health benefits.
According to Wikipedia:
Clitoria ternatea, common names including butterfly pea, blue pea, Aprajita, Cordofan pea and Asian pigeonwings, is a plant species belonging to the Fabaceae family.
......Names in other languages include bunga telang (Malay), อัญชัน `anchan (Thai), đậu biếc (Vietnamese), अपराजिता Aparajita in Hindi and 蝶豆 dié dòu (Mandarin Chinese), 'Sankhu Poolu/Sankham Poolu' in Telugu, "Shankupushpam" in Malayalam language and অপরাজিতা (Aparajita) in Bengali.
In Thailand, a syrupy blue drink is made called nam dok anchan (น้ำดอกอัญชัน), it is sometimes consumed with a drop of sweet lime juice to increase acidity and turn the juice into pink-purple.