The invention relates to a composition comprising: i) at least one oxidation base, preferably of heterocyclic and/or para-phenylenediamine type; and ii) at least one heteroaryl coupler of formula (I), with R1, R2, R3, A and X as defined in the description. The invention also relates to a process for dyeing keratin fibres using ingredients i) and ii); to a kit comprising ingredients i) and ii); and to the use of ingredient i) combined with ii) for dyeing keratin fibres. The composition of the invention leads to particularly powerful, chromatic and sparingly selective colourings.