A solution turns red litmus blue and turns phenolphthalein solution pink. The solution is a acid or a base?
Indicators
Indicators are used to identify whether the given substance is acid or base.
Phenolphthalein is an organic compound and is used as an acid-base indicator.
The indicator phenopthaline gives pink color to acid solution and is colorless in an acidic medium.
Litmus paper
Hence, the solution is a base.