Why does baking soda make water turn blue?

However, there are a few experiments you can do with baking soda and water that lead to a variety of color changes:

- Add baking soda to red cabbage juice: Red cabbage juice contains a natural indicator called anthocyanin, which changes color depending on the pH of the solution. Adding baking soda (a base) to red cabbage juice will cause the pH to increase and the solution will turn blue.

- Add baking soda to a mixture of vinegar and phenolphthalein: Phenolphthalein is a colorless indicator that turns pink when the pH of the solution is 8.3 or higher. Adding baking soda (a base) to a mixture of vinegar and phenolphthalein will cause the pH to increase and the solution will turn pink.

- Add baking soda to a solution of copper sulfate: Copper sulfate is a blue compound that dissolves in water. Adding baking soda (a base) to a solution of copper sulfate will cause the copper ions to precipitate out of the solution and the water will turn clear.