Chlorophyll contained in vegetables will react with iron ions and turn yellow, which can be avoided by adding water appropriately.

When cooking, you can add some water to the pot, which can reduce the concentration of iron ions in vegetables and avoid combining with chlorophyll.

When cooking, you can add some alkaline seasonings, such as soy sauce and white vinegar, which can also reduce the concentration of iron ions in vegetables and avoid combining with chlorophyll.

When cooking, you can add some antioxidants, such as vitamin C, which can also effectively prevent vegetables from turning yellow.

When washing vegetables, you can soak them in soda water or lemon juice for a while, which will also help prevent them from turning yellow.

When cooking, you can cut vegetables into small pieces, which can reduce the concentration of iron ions in vegetables and avoid combining with chlorophyll.