Question

How do acid base indicators change color?

Answer 1

Acid-base indicators will have protons either added or removed to them depending on the pH level. These changes will cause the indicator to change color.

Explanation:

The video below shows an experiment using an indicator derived from boiling red cabbage. A pigment from the cabbage called anthocyanin is what causes all of the different colors you see.

Other common indicators include:
bromothymol blue
thymol blue
methyl orange
bromocresol green
methyl red
phenol red

Hope this helps!