What are substances called that change color when added to acids or bases?

Substances that change color when added to acids or bases are known as indicators. These compounds are typically weak acids or bases themselves that undergo a structural change when the pH of the solution changes. This structural change results in a different color manifestation, providing a visual cue that can help determine the acidity or basicity of a solution. Common examples of indicators include phenolphthalein, which turns pink in basic solutions, and litmus, which changes from red to blue when moving from acidic to basic conditions.

In contrast, electrolytes are substances that dissociate into ions in solution and conduct electricity, but they do not have the color-changing properties associated with pH changes. Insulators are materials that do not conduct electricity, while capacitors are components used in electrical circuits to store energy, neither of which pertains to the color change characteristic typical of indicators in the context of acids and bases.