The color of purple potato is due to anthocyanin, which is purple in neutral environment, purple in acidic environment and blue in alkaline environment. Generally cooked purple potato porridge and the like can easily turn blue or even green due to water or other reasons. Just add a little acid liquid such as white vinegar or lemon juice to change it back to purple.
The main source of anthocyanins
Anthocyanins widely exist in flowering plants (angiosperms), and their contents in plants vary greatly with varieties, seasons, climate and maturity.
According to preliminary statistics, there are 27 families and 73 genera of plants, such as purple sweet potato, grape, blood orange, cabbage, blueberry, eggplant, cherry, cranberry, strawberry, mulberry, hawthorn and morning glory.