When blue litmus paper dipped acids, its colour changes to ____?

1. Pink
2. Blue
3. Yellow
4. Red

Litmus paper is a common pH indicator. Blue litmus paper is used to test for acids. When dipped into an acidic solution (pH < 7), blue litmus paper turns red. This color change is a standard test for acidity. It turns blue in basic solutions and remains blue in neutral solutions.