Answer:
Red litmus paper would turn blue when in contact with a base.
Step-by-step explanation:
Litmus paper is a test used to show whether a substance is an acid or a base. However it simply shows whether it is an acid or a base and does not show how acidic or alkaline a substance is.
Blue litmus paper turns red under acidic conditions.
Red litmus paper on the other hand turns blue under alkaline conditions.