Lightening/coloring of keratin fibers, preferably human keratin fibers such as hair, comprises applying an aqueous cosmetic composition (A) comprising one or more fatty substances and one or more surfactants； a cosmetic composition (B) comprising one or more alkaline agents； and a composition (C) comprising one or more oxidizing agents, one the keratin fibers, where the amount of the fatty substance of composition (A) is greater than 20 wt.%, when the process is for dyeing keratin fibers, and the cosmetic composition (B) further comprises one or more oxidation dyes and/or direct dyes. An independent claim is included for a multi-compartment device comprising first compartment containing the composition (A) a second compartment containing the composition (B) with one or more oxidation dyes and/or direct dyes, and one or more alkaline agents, and a third compartment containing the composition (C) comprising one or more oxidation agent.
