A method of colouring porous material, especially human hair, is described, which method comprises applying to the material being coloured, in any desired order successively, or simultaneously, a) at least one capped diazonium compound of Formula (1) and/or at least one compound of Formula (2) and/or at least one compound of Formula (3) wherein Q is an unsubstituted or substituted aromatic or heterocyclic residue, R is the radical of an unsubstituted or substituted, water-soluble aliphatic or aromatic amine, and T is an unsubstituted or substituted, water-soluble aliphatic or aromatic residue, wherein at least one of the groups must contain a radical imparting water solubility, and a) at least one water-soluble coupling component under conditions such that, initially, coupling does not take place, and then causing the capped diazonium compound present on the material to react with the coupling component