Here's why:

* pH paper is designed to change color depending on the acidity or alkalinity (basicity) of a solution.

* Acidic solutions turn pH paper red.

* Basic (alkaline) solutions turn pH paper blue.

* Neutral solutions are neither acidic nor basic, and they turn pH paper green.

Therefore, a greenish color on pH paper indicates a substance with a pH close to 7, which is considered neutral.

Examples of neutral substances:

* Pure water

* Salt solutions (like table salt in water)

Let me know if you have any other questions!