Process for coloring keratin fibers comprises treating the fibers with (i) one or more orthodiphenol derivatives, (ii) one or more metal salts, (iii) hydrogen peroxide or one or more hydrogen peroxide generating system, and (iv) one or more (bi)carbonates, provided that when the process implements one or more hydrogen peroxide generating system, the process is carried out in several stages and/or the bicarbonate can not be applied together on the fibers with metal salt. Independent claims are included for: (1) a cosmetic composition for coloring keratin fibers containing (i) one or more orthodiphenol derivatives, (ii) one or more metal salts, (iii) hydrogen peroxide or one or more system for generating hydrogen peroxide and (iv) one or more bicarbonates; and (2) a device having many compartments comprising 2 to 5 compartments containing 2 to 5 compositions in which the ingredients (i), (ii), (iii) and (iv) are distributed, and the compositions are aqueous or powdery, with at least one of these compositions be
