What color does tonic water change to when adding cabbage juice?

Here's why:

* Cabbage juice is a natural pH indicator. It contains pigments called anthocyanins that change color depending on the acidity or alkalinity of the solution.

* Tonic water is slightly acidic. This is due to the quinine it contains.

* In acidic solutions, anthocyanins turn red. So, when you add cabbage juice to tonic water, the anthocyanins in the cabbage juice react with the acidic tonic water and change color to a pinkish-red.