Coloring keratinous fibers, preferably human keratinous fibers such as hair, comprises treating keratinous fibers with cosmetic composition including (a) naphthol derivative, (b) magnesium salt or zinc salt, (c) hydrogen peroxide, (d) bicarbonates and (e) optionally alkalizing agent different from bicarbonate. An independent claim is included for a device comprising compartments in which the ingredients of composition are distributed.