Use of specific heterocyclic couplers which are 7-amino-1,2,3,4-tetrahydroquinoline derivatives of formula and also the salts thereof with an organic or inorganic acid or base, the optical or geometric isomers thereof and/or the solvates thereof such as the hydrates: in which formula: • R 1, R 2, R 3, R 4, R 5 and R 6, which may be identical or different, represent a hydrogen or halogen atom; a linear or branched C 1 -C 6 alkyl radical optionally substituted with one or more hydroxyl groups, preferably with a single hydroxyl group; a carboxyl radical; a (C 1 -C 6)alkoxycarbonyl radical -C -O-R with R representing a linear or branched C 1 -C 6 alkyl radical; an alkylcarbonyloxy radical -O-C -R with R being as defined previously; preferably, R 1, R 2, R 3, R 4, R 5 and R 6, which may be identical or different, represent a hydrogen atom or a C 1 -C 4 alkyl radical; • R a, R b and R c, which may be identical or different, represent a hydrogen or halogen atom or a C 1 -C 6 alkyl radical; preferably, R a, R b and R c are identical and represent a hydrogen atom; • X represents i) an amino radical -NT 1 T 2, ii) an aminoalkylamino radical -N(T 3)-L-NT 1 T 2 or iii) an oxyalkylamino radical -O-L-NT 1 T 2; • T 1 and T 2, which may be identical or different, represent a linear or branched C 1 -C 6 alkyl radical optionally substituted with one or more hydroxyl radicals, preferably with a single hydroxyl group; • or else T 1 and T 2 together form, with the nitrogen atom to which they are attached, a saturated or unsaturated heterocycle comprising 5 to 7 members, one of the members of which may be a heteroatom chosen from O, S and N; it being possible for said heterocycle to be optionally substituted with one or more linear or branched C 1 -C 4 alkyl or linear or branched C 1 -C 4 hydroxyalkyl radicals; • T 3 represents a hydrogen atom or a linear or branched C 1 -C 6 alkyl radical optionally substituted with one or more hydroxyl radicals, preferably with a single hydroxyl group; • L represents a linear or branched, saturated C 1 -C 10 alkylene hydrocarbon-based chain optionally substituted with one or more hydroxyl radicals, preferably with a single hydroxyl group; for dyeing keratin fibres. • R 1, R 2, R 3, R 4, R 5 and R 6, which may be identical or different, represent a hydrogen or halogen atom; a linear or branched C 1 -C 6 alkyl radical optionally substituted with one or more hydroxyl groups, preferably with a single hydroxyl group; a carboxyl radical; a (C 1 -C 6)alkoxycarbonyl radical -C -O-R with R representing a linear or branched C 1 -C 6 alkyl radical; an alkylcarbonyloxy radical -O-C -R with R being as defined previously; preferably, R 1, R 2, R 3, R 4, R 5 and R 6, which may be identical or different, represent a hydrogen atom or a C 1 -C 4 alkyl radical; • R a, R b and R c, which may be identical or different, represent a hydrogen or halogen atom or a C 1 -C 6 alkyl radical; preferably, R a, R b and R c are identical and represent a hydrogen atom; • X represents i) an amino radical -NT 1 T 2, ii) an aminoalkylamino radical -N(T 3)-L-NT 1 T 2 or iii) an oxyalkylamino radical -O-L-NT 1 T 2; • T 1 and T 2, which may be identical or different, represent a linear or branched C 1 -C 6 alkyl radical optionally substituted with one or more hydroxyl radicals, preferably with a single hydroxyl group; • or else T 1 and T 2 together form, with the nitrogen atom to which they are attached, a saturated or unsaturated heterocycle comprising 5 to 7 members, one of the members of which may be a heteroatom chosen from O, S and N; it being possible for said heterocycle to be optionally substituted with one or more linear or branched C 1 -C 4 alkyl or linear or branched C 1 -C 4 hydroxyalkyl radicals; • T 3 represents a hydrogen atom or a linear or branched C 1 -C 6 alkyl radical optionally substituted with one or more hydroxyl radicals, preferably with a single hydroxyl group; • L represents a linear or branched, saturated C 1 -C 10 alkylene hydrocarbon-based chain optionally substituted with one or more hydroxyl radicals, preferably with a single hydroxyl group;