Answer:
Acids turn litmus paper red.
Explanation:
When exposed to solutions under a pH of 7, it turns red because the solution is acidic. When exposed to a solution that has a higher pH of 7 or above, the solution is alkaline, and it turns litmus paper blue. If the solution is neutral,
( pH of 7 ) then the litmus paper will turn purple.
What you are looking for is ACID so the litmus paper will turn RED.