<p>A method for colouring hair, comprising the step of applying to the hair a composition comprising a dye polymer in which the dye polymer is obtainable by the reaction of a NH2 group directly and covalently bound to an aromatic ring of a dye i) with a reactive group of a monomeric compound ii) in which the reactive group is selected from the group consisting of isocyanate; oxazolone; ester and epoxide, followed by polymerising the resulting dye monomer to form a dye polymer iii).</p>
