A hair and/or scalp treatment composition comprising an amino-oxo-indole-ylidene compound of general formula (I): (I) fourmula should be here in which:R1, R2, R3 and R4 are each, independently, hydrogen or a monovalent organicgroup selected from alkyl, alkenyl, alkynyl, aryl, alkylenearyl, cycloalkyl,cycloalkenyl, and heterocyclyl.