Used as a redox indicator in analytical chemistry, particularly in titrations involving oxidizing and reducing agents. It remains colorless in its reduced (leuco) form and turns blue upon oxidation, making it useful for detecting the endpoint in redox reactions. Commonly applied in biochemical assays and enzymatic studies where visual monitoring of electron transfer is required. Also utilized in some dye-sensitized electrochemical sensors and as a mediator in certain types of biosensors.