An agent for coloring and optionally simultaneously lightening keratin fibers, in particular human hair, containing, in a cosmetic carrier (a) at least one compound of formula where R1, R2, R3 each represent, independently of one another, hydrogen, halogen, a nitro group, a cyano group, a carboxyl group, a sulfonic acid group, a hydroxy group, a C 1 -C 6 acyl amino group, a carboxamide group, a sulfonamide group, a C 1 -C 6 alkyl group, C 1 -C 6 alkoxy group, a C 2 -C 6 alkenyl group, a C 2 -C 6 hydroxyalkyl group or a C 1 -C 6 alkoxy-C 2 -C 6 alkyl group; R4, R5, R6 each represent, independently of one another, a C 1 -C 6 alkyl group, a C 2 -C 6 alkenyl group, a C 2 -C 6 hydroxyalkyl group or a C 1 -C 6 alkoxy-C 2 -C 6 alkyl group; or R4 and R5, together with the quaternary nitrogen atom to which they are bound, form a 5-, 6- or 7-membered ring, which can optionally contain additional heteroatoms and/or can carry additional substituents; X, Y, Z each represent, independently of one another, hydrogen, a hydroxy group or an N group, where R7 and R8 each represent, independently of one another, hydrogen, a C 1 -C 6 alkyl group, a C 2 -C 6 alkenyl group, a C 2 -C 6 hydroxyalkyl group or a C 1 -C 6 alkoxy-C 2 -C 6 alkyl group, with the proviso that at least one of the functional groups X, Y, Z represents an N group, n represents a number from 2 to 6, A - represents a physiologically acceptable anion, and (b) at least one fatty acid diester of an alkane diol, wherein the agent contains the fatty acid diester(s) of an alkane diol (b) in a proportion of from 0.5 to 5.0 wt.%, in each case based on the total weight of the agent. (a) at least one compound of formula where R1, R2, R3 each represent, independently of one another, hydrogen, halogen, a nitro group, a cyano group, a carboxyl group, a sulfonic acid group, a hydroxy group, a C 1 -C 6 acyl amino group, a carboxamide group, a sulfonamide group, a C 1 -C 6 alkyl group, C 1 -C 6 alkoxy group, a C 2 -C 6 alkenyl group, a C 2 -C 6 hydroxyalkyl group or a C 1 -C 6 alkoxy-C 2 -C 6 alkyl group; R4, R5, R6 each represent, independently of one another, a C 1 -C 6 alkyl group, a C 2 -C 6 alkenyl group, a C 2 -C 6 hydroxyalkyl group or a C 1 -C 6 alkoxy-C 2 -C 6 alkyl group; or R4 and R5, together with the quaternary nitrogen atom to which they are bound, form a 5-, 6- or 7-membered ring, which can optionally contain additional heteroatoms and/or can carry additional substituents; X, Y, Z each represent, independently of one another, hydrogen, a hydroxy group or an N group, where R7 and R8 each represent, independently of one another, hydrogen, a C 1 -C 6 alkyl group, a C 2 -C 6 alkenyl group, a C 2 -C 6 hydroxyalkyl group or a C 1 -C 6 alkoxy-C 2 -C 6 alkyl group, with the proviso that at least one of the functional groups X, Y, Z represents an N group, n represents a number from 2 to 6, A - represents a physiologically acceptable anion, and R1, R2, R3 each represent, independently of one another, hydrogen, halogen, a nitro group, a cyano group, a carboxyl group, a sulfonic acid group, a hydroxy group, a C 1 -C 6 acyl amino group, a carboxamide group, a sulfonamide group, a C 1 -C 6 alkyl group, C 1 -C 6 alkoxy group, a C 2 -C 6 alkenyl group, a C 2 -C 6 hydroxyalkyl group or a C 1 -C 6 alkoxy-C 2 -C 6 alkyl group; R4, R5, R6 each represent, independently of one another, a C 1 -C 6 alkyl group, a C 2 -C 6 alkenyl group, a C 2 -C 6 hydroxyalkyl group or a C 1 -C 6 alkoxy-C 2 -C 6 alkyl group; or R4 and R5, together with the quaternary nitrogen atom to which they are bound, form a 5-, 6- or 7-membered ring, which can optionally contain additional heteroatoms and/or can carry additional substituents; X, Y, Z each represent, independently of one another, hydrogen, a hydroxy group or an N group, where R7 and R8 each represent, independently of one another, hydrogen, a C 1 -C 6 alkyl group, a C 2 -C 6 alkenyl group, a C 2 -C 6 hydroxyalkyl group or a C 1 -C 6 alkoxy-C 2 -C 6 alkyl group, with the proviso that at least one of the functional groups X, Y, Z represents an N group, n represents a number from 2 to 6, A - represents a physiologically acceptable anion, (b) at least one fatty acid diester of an alkane diol, wherein the agent contains the fatty acid diester(s) of an alkane diol (b) in a proportion of from 0.5 to 5.0 wt.%, in each case based on the total weight of the agent.