The present invention relates to a process for dyeing keratin fibres, in particular human keratin fibres such as the hair, in which the said fibres are treated using one or more cosmetic compositions comprising a) one or more ortho-diphenols, b) one or more organic salts of titanium and of at least one carboxylic acid, and c) optionally one or more chemical oxidizing agents such as hydrogen peroxide or one or more hydrogen peroxide generating systems.