Question

Why do visual indicators show a change in colour when introduced to an acidic and basic medium?

Answer 1

The color change of a indicator is caused by the dissociation of the H⁺ ion from the indicator itself. The change in concentration triggers change in colour.
This colour will depend on the type of indicators.
Eg:Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions