Used in hair dye formulations as a coupler to produce stable, long-lasting color tones, particularly in permanent and oxidative dyes. It reacts with primary intermediates like p-phenylenediamine in the presence of hydrogen peroxide to form larger colored molecules within the hair shaft. Offers good color intensity and can help achieve natural-looking shades, especially in brown and black dye systems. Also valued for its relatively low skin irritation potential compared to other amino-substituted pyrimidines.