Cosmetic agents for treating keratinic fibers and methods for the reductive decolorization of dyed keratinic fibers are provided herein. In an embodiment, a cosmetic agent for treating keratinic fibers includes (a) one or more metal salts chosen from the group of tin(II) salts, iron(II) salts, manganese(II) salts, titanium(II) salts, or titanium(III) salts and (b) water. The agent has a pH between about 1.0 and about 3.0.