Why did my boiled chicken turn grey?

Boiled chicken can turn grey due to a chemical reaction between the proteins and oxygen. This process is called oxidation and it occurs when the chicken is exposed to air. It can also be caused by overcooking the chicken, as this can cause the proteins to break down and release pigments that can give the chicken a grey colour. To avoid this, you can cook the chicken on a lower heat and make sure to not overcook it. You can also try adding some acid, such as lemon juice or vinegar, to the cooking water to help prevent the chicken from turning grey.