Question

how they change their colour in acidic or basic medium​

Answer 1

Answer:

it is because

Explanation:

The main use of litmus is to test whether a solution is acidic or basic. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F). Neutral litmus paper is purple.[1] Litmus can also be prepared as an aqueous solution that functions similarly. Under acidic conditions, the solution is red, and under alkaline conditions, the solution is blue.

Answer 2

Explanation:

Universal indicator has many different colour changes, from red for strongly acidic solutions to dark purple for strongly alkaline solutions. In the middle, neutral pH 7 is indicated by green.