Using red cabbage as an indicator -Place 5 mL of known pH solutions in each of your labelled test tubes. To these, add 5 drops of red cabbage indicator. You are now ready to compare your unknowns with your knowns by placing 5 mL of an unknown into a clean test tube, adding 5 drops of red cabbage juice and comparing the unknown with your knowns. As all titrations that this writer is familiar with use phenolphthalein as an indicator, there is no reason for not using red cabbage instead. Cabbage juice appears to be a useful indicator, as do other some naturally colored materials.
Materials serve best within specific pH ranges.