The object of the present invention are diketopyrrolopyrroles of the general formula (I) ##STR1## wherein, independently of one another, Q.sub.1 and Q.sub.2 represent an optionally substituted, aromatic, isocyclic or heterocyclic group with 5 to 14 atoms in the ring, the heterocyclic group containing at least one oxygen, nitrogen or sulfur atom, and the R1 and R2 groups, independently of one another represent hydrogen or a Y--B.sup.+ A.sup.- group, with the proviso that at least one of the R1 and R2 groups is not hydrogen; B.sup.+ is an aromatic, aliphatic, alicyclic, aromatic heterocyclic or non-aromatic heterocyclic, quaternary ammonium group or a quaternary phosphonium group; Y is an optionally substituted linear or branched C.sub.1 to C.sub.6 alkylene group and A.sup.- is an anion; a method for their synthesis as well as agents, containing compounds of formula (I), for dyeing keratin fibers.