A cosmetic agent for color modification of keratinic fibres comprising a cosmetically acceptable carrier； at least one compound selected form oxidation dye precursors, direct dyes and mixtures thereof； and a quaternized copolymer of vinylpyrrolidone and dimethylaminoethyl methacrylate. Preferably, the copolymer is quaternized with diethyl sulfate, known as polyquaternium-11. The composition may also comprise an alcohol having 8-20 carbon atoms, preferably 2-octyldodecanol and/or cetearyl alcohol. The composition may also comprise partial esters and/or polyol partial esters, e.g. glycerol monostearate. Also disclosed is a packaging unit comprising, produced separately from one another, at least one container containing said cosmetic agent, and at least one container containing an oxidising agent preparation, which in a cosmetically acceptable carrier contains at least one oxidising agent and at least one acid. Further disclosed is a method for dyeing keratinic fibres comprising the steps of mixing said cosmetic agent and said oxidising agent preparation, applying the mixture to the keratinic fibres and leaving for 1-60 minutes then rinsing the fibres with water and/or a cleaning composition. The claimed invention leads to improved conditioning, in particular to an increased volume of the keratinic fibres, preferably human hair, with a simultaneously minimised color shift.
