A multi-component packaging unit (kit-of-parts) for the reductive bleaching of colored keratin fibers which contains, in separately manufactured form, (I) a first container (A) containing a cosmetic agent (a) and ( II) a second container (B) containing a cosmetic agent (b) and (III) a third container (C) containing a cosmetic agent (c), the agent (a) of the container (A) containing (a1) one or several reducing agents selected from the group consisting of formamidine-sulfinic acid, sodium dithionite, zinc dithionite, potassium dithionite, hydroxymethanesulfinic acid, aminomethanesulfinic acid, cysteine, thiolactic acid, sulfanylacetic acid (thioglycolic acid) and / or ascorbic acid, and the agent (b) of the container (B) containing (b1) one or more oxidizing agents of the group comprising hydrogen peroxide, the potassium persulfate, sodium persulfate and / or persulfa ammonium, and the agent (c) of the container (C) containing (c1) one or more basifying agents, the ratio by weight of the total amount of all the reducing agents (a1) contained in the agent (a) ) to the total amount of all oxidizing agents (b1) contained in agent (b) having a value of 50.0 to 4.0 based on the total weight of the agents (a) plus (b) plus (c) ). Other objects of the present invention are a ready-to-use bleaching agent and a reductive bleaching process of keratin fibers stained with the multicomponent packaging unit. Unité d'emballage à plusieurs composants (kit-of-parts) destinée à la décoloration réductrice de fibres de kératine colorées qui contient, sous forme confectionnée séparément, (I) un premier récipient (A) contenant un agent cosmétique (a) et (II) un deuxième récipient (B) contenant un agent cosmétique (b) et (III) un troisième récipient (C) contenant un agent cosmétique (c), l'agent (a) du récipient (A) contenant (a1) un ou plusieurs agents réducteurs choisis dans le groupe constitué par l'acide formamidine-sulfinique, le dithionite
