Method: chop the cabbage into small pieces until you have enough to fill 2 cups. Place the cabbage in a large beaker and add water to cover the cabbage. Boil over a Bunsen burner for at least ten minutes for the color to leach out of the cabbage. Filter out the plant material to obtain a red-purple-bluish colored liquid. This liquid is at about pH 7. (The exact color you get depends on the pH of the water.) Place a small beaker and leave to one side. Repeat this method for the beetroot.
Result: