1, the purple potato porridge will become blue-green because the purple potato is rich in anthocyanins, anthocyanins in the neutral environment is purple, acidic environment is purple red, alkaline environment on the blue, the general cooking out of the purple potato porridge and so on due to the water or other reasons it is very easy to become blue or even with green.

2, this is a normal phenomenon, you can rest assured that the food, just need to add a little white vinegar or lemon juice and other acidic liquids can be changed back to purple.