What substance does purple cabbage indicator actually test for?

The substance that purple cabbage indicator actually test for is pH (acidity or alkalinity). It is a natural pH indicator that changes colour depending on the acidity or alkalinity of the solution it is added to. In acidic solutions, purple cabbage indicator turns red, while in alkaline solutions, it turns green or blue. The intensity of the colour change also increases with increasing acidity or alkalinity. This makes purple cabbage indicator a useful tool for estimating the pH of a solution without the need for expensive or specialized equipment.