How do indicators work in acid base reactions?
Indicators a mostly the organic compound which change their functional groups' structures in different media by changing their colors. So, in acid base reactions acidic media is changed to basic or reverse happens, and this media causes the color change in indicators.
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:
Hope this helps!