What color does litmus turn in acidic solutions?

In acidic solutions, litmus paper changes color to red. This behavior is part of its role as a pH indicator. Litmus is a natural dye derived from lichens and it helps to determine the acidity or basicity of a solution. When in an acidic environment (pH less than 7), the chemical structure of the dye changes, causing it to exhibit a red color.

In contrast, in alkaline solutions, litmus turns blue. The other colors mentioned, green and yellow, do not correspond to litmus reactions; green typically results from a neutral pH with a mix of red and blue, while yellow is not relevant to litmus paper's color indicators. Thus, the correct answer reflects the specific response of litmus in acidic conditions, reinforcing its utility as a simple and effective pH indicator.