Used in hair dye formulations as a coupler to produce permanent and oxidative color shades, particularly contributing to warm brown and auburn tones. It reacts with primary intermediates like p-phenylenediamine in the presence of hydrogen peroxide to form larger colored molecules within the hair shaft. Its methoxy group helps stabilize the dye intermediate and influences hue, while the amino group enables coupling reactions. Due to its sensitivity to oxidation and pH, it is often stabilized in hydrochloride form for improved shelf life and solubility in aqueous dye systems.