The structure of a colored intermediate commonly formed in the oxidation of p-aminophenol at low pH is established by analysis of H NMR and UV/vis spectra, kinetics, and molecular modeling, following a new method for synthesizing the dye in high concentrations. The chromogen is shown to consist of two compounds with absorption maxima at 540-560 and 375-385 nm. The 2,6-dimethyl and 3,5-dimethyl analogues of p-aminophenol are found to undergo N-rather than C-substitution under similar conditions.