Composition comprising: i) at least one oxidation base preferably chosen from heterocyclic bases and para-phenylenediamine bases; ii) at least one heteroaryl coupler of formula (I'): and also addition salts thereof with an organic or mineral acid or base, optical or geometrical isomers thereof, tautomers thereof or solvates thereof such as hydrates, in which compound of formula (I'): • R 1 and R 2 , which may be identical or different, represent i) a linear or branched (C 1 -C 4 ) alkyl group, optionally interrupted with one or more heteroatoms, and optionally hydrogenated or (C 1 -C 4 )alkylated, and/or optionally substituted, ii) optionally substituted aryl; iii) optionally substituted heteroaryl; iv) optionally substituted (hetero)cycloalkyl; or alternatively R 1 and R 2 form, together with the nitrogen atom that bears them, an optionally substituted heterocycloalkyl, also possibly comprising one or more heteroatoms chosen from oxygen, sulfur and nitrogen, said heterocycle preferentially being 5- or 6-membered such as morpholino, piperazino or piperidino; • R 3 represents i) a linear or branched (C 1 -C 4 ) alkyl group, optionally interrupted with one or more heteroatoms, and optionally hydrogenated or (C 1 -C 4 )alkylated, and/or optionally substituted with one or more groups; ii) optionally substituted aryl; iii) optionally substituted heteroaryl or iv) optionally substituted (hetero)cycloalkyl. i) at least one oxidation base preferably chosen from heterocyclic bases and para-phenylenediamine bases; ii) at least one heteroaryl coupler of formula (I'): and also addition salts thereof with an organic or mineral acid or base, optical or geometrical isomers thereof, tautomers thereof or solvates thereof such as hydrates, in which compound of formula (I'): • R 1 and R 2 , which may be identical or different, represent i) a linear or branched (C 1 -C 4 ) alkyl group, optionally interrupted with one or more heteroatoms, and optionally hydrogenated or (C 1 -C 4 )alkylated, and/or optionally substituted, ii) optionally substituted aryl; iii) optionally substituted heteroaryl; iv) optionally substituted (hetero)cycloalkyl; or alternatively R 1 and R 2 form, together with the nitrogen atom that bears them, an optionally substituted heterocycloalkyl, also possibly comprising one or more heteroatoms chosen from oxygen, sulfur and nitrogen, said heterocycle preferentially being 5- or 6-membered such as morpholino, piperazino or piperidino; • R 3 represents i) a linear or branched (C 1 -C 4 ) alkyl group, optionally interrupted with one or more heteroatoms, and optionally hydrogenated or (C 1 -C 4 )alkylated, and/or optionally substituted with one or more groups; ii) optionally substituted aryl; iii) optionally substituted heteroaryl or iv) optionally substituted (hetero)cycloalkyl. • R 1 and R 2 , which may be identical or different, represent i) a linear or branched (C 1 -C 4 ) alkyl group, optionally interrupted with one or more heteroatoms, and optionally hydrogenated or (C 1 -C 4 )alkylated, and/or optionally substituted, ii) optionally substituted aryl; iii) optionally substituted heteroaryl; iv) optionally substituted (hetero)cycloalkyl; or alternatively R 1 and R 2 form, together with the nitrogen atom that bears them, an optionally substituted heterocycloalkyl, also possibly comprising one or more heteroatoms chosen from oxygen, sulfur and nitrogen, said heterocycle preferentially being 5- or 6-membered such as morpholino, piperazino or piperidino; • R 3 represents i) a linear or branched (C 1 -C 4 ) alkyl group, optionally interrupted with one or more heteroatoms, and optionally hydrogenated or (C 1 -C 4 )alkylated, and/or optionally substituted with one or more groups; ii) optionally substituted aryl; iii) optionally substituted heteroaryl or iv) optionally substituted (hetero)cycloalkyl. <EOS>