Why must an indicator's color-change range overlap the equivalence point pH of a titration?

Core Concept

An indicator is itself a weak acid whose protonated and deprotonated forms show different colors, switching across a range centered on its own pKa. The visible switch defines the endpoint of the titration, so that switch must occur where the equivalence point falls. Without overlap, the endpoint signals a pH far from stoichiometric completion and the recorded volume is wrong.