An agent for dyeing keratin fibers comprises a composition A comprising at least one alkalizing agent, at least one oxidative dye precursor, at least one surfactant and at least one fatty substance free of carboxylic acid groups and a composition B comprising at least one oxidizing agent and at least one surfactant. The concentration of fatty substances free of carboxylic acid groups after mixing composition A and composition B is at least 20% by weight relative to the total weight of the mixed composition A and B. The concentration of alkalizing agent after mixing composition A and composition B is not more than 1.75% by weight relative to the total weight of the mixed composition A and B.
