A multi-component packaging unit (kit-of-parts) for reductively decolouring dyed keratin fibres, particularly human hair, which comprises a container (A) containing a cosmetic agent (a) and a container (B) containing a cosmetic agent (b), which are produced separately from each other, wherein agent (a) contains one or more sulfur-containing reductants and agent (b) contains one or more metal salts from the group of the tin(II) salts, the iron(II) salts, the manganese(II) salts, the titanium(II) salts, and the titanium(III) salts. The sulfur containing reductant may be formamidine sulfinic acid (thiourea dioxide). The metal salt may be tin(II) fluoride, tin(II) chloride or iron(II) chloride. Cosmetic agent (a) may also contain one or more fatty constituent. The kit-of-parts may also comprise a container (C) containing a cosmetic agent (c) which may comprise one or more acids or alkalizing agents. The invention also relates to a method for reductively decolouring dyed keratin fibres comprising the following steps: producing a ready-to-use decolouring agent by mixing (a) and (c)； applying the ready-to-use decolouring agent to keratin fibres； allowing the decolouring agent to act； optionally, rinsing the decolouring agent off； applying (b) to the keratin fibres； allowing (b) to act and, optionally, rinsing (b) off the fibres.
