Disclosed are oligomeric cationic azo dyes of formula (I), wherein their salts, isomers, hydrates and other solvates, wherein R1 is hydrogen C1-C12alkyl, which may be substituted by one or more C1-C5alkyl, C1-C5-alkoxy, hydroxy or -(CO)-H -(CO)-C1-C5alkyl phenyl or phenyl-C1-C4alkyl, wherein the phenyl moiety may be substituted by one or more C1-C5alkyl, C1-C5alkoxy, halogen, -NH2, mono-C1-C5alkylamino, di-C1-C5alkylamino, -NO2, carboxy or hydroxy R2 is hydrogen or C1-C5alkyl X is C1-C10alkylene, which may be substituted by one or more C1-C5alkyl, hydroxy, C1-C5-alkoxy, amino, mono-C1-C5alkylamino, di-C1-C5alkylamino, -SH, and/or interrupted by one or more -O- or -S-S- C5-C10cycloalkylene C5-C12arylene C5-C12arylene-(C1-C10alkylene) biphenylene, which may be substituted by one or more C1-C5alkyl, hydroxy, C1-C5-alkoxy, amino, mono-C1-C5alkylamino, di-C1-C5alkylamino, -SH, and/or interrupted by one or more -O-, C1-C4-alkylene, -NR3-, -S- or -S-S- R3 is hydrogen C1-C12alkyl C2-C14alkenyl C6-C12aryl C6-C12aryl-C1-C12alkyl or C1-C12alkyl-C6-C12aryl Y is an anion Z is 1,3-thiazolyl 1,2-thiazolyl 1,3-benzothiazolyl 2,3-benzothiazolyl imidazolyl 1,3,4-thiadiazolyl 1,3,5-thiadiazolyl 1,3,4-triazolyl pyrazolyl benzimidazolyl benzopyrazolyl pyridinyl quinolinyl pyrimidinyl or isoxazolyl and n is a number from 2-100. Furthermore, the present invention relates to novel cationic oligomeric azo dyes, compositions thereof, especially comprising other dyes, and to application for hair dying.L’invention concerne des colorants azoïques cationiques oligomériques de formule (I), leurs sels, isomères, hydrates et autres solvates, où R1 est un hydrogène, un alkyle en C1-C12, lequel peut être substitué par un ou plusieurs alkyles en C1-C5, alcoxy en C1-C5, hydroxy ou -(CO)-H un -(CO)-(alkyle en C1-C5) un phényle ou un phényl(alkyle en C1-C4), le fragment phényle pouvant être substitué par un ou plusieurs alkyles en C1-C5, alcoxy en C1-C5, halogènes, -NH2, mono(alkyl en C1-C5)amino, di(a
