The present invention relates to a process for dyeing human keratin fibers comprising applying to said fibers: - at least one composition (a) comprising - at least one compound of the family of iridoids of formulae defined, at least one second compound chosen from among the amines and a third carbonyl compound, the composition (a) having a ph of less than or equal to 9.5, and - at least one composition (b) comprising at least one oxidizing agent, the composition b is applied after a leave-in time of at least 15 minutes after application of the composition.
