An active agent combination of (a) at least one water-soluble polymer comprising at least one *—Si(OR)x(R′)3-x residue, in which R and R′, independently of one another, denote a (C1 to C4)alkyl group, and x denotes 1, 2 or 3, and (b) at least one polar alkoxysilane compound of formula (SI), in which G denotes a (C1 to C3)alkylene group, K″ denotes a connectivity selected from a covalent bond or from a molecular fragment having two free valences, R1 denotes a molecular fragment comprising at least one polar substituent selected from the group consisting of quaternized nitrogen atoms, amino groups, anionic residues, and combinations thereof, x denotes 1, 2 or 3, R and R′, independently of one another, denote a (C1 to C4)alkyl group, is suitable for improving synthetic colorings of coloring compounds on keratin-containing fibers.
