Process for colouring hair keratin fibers, comprising the application of a composition A and a composition B to said hair keratin fibers, in which:
- composition A comprises at least one (poly)carbodiimide compound, and
- composition B comprises:
- at least one associative polymer;
- at least one compound, different from the associative polymers, containing at least one carboxylic acid group;
- and
- at least one compound, preferably at least two compounds, containing at least one hydroxyl function;
- composition A and/or composition B comprising at least one colouring agent chosen from pigments, direct dyes and mixtures thereof, and
- in which composition A and composition B are applied simultaneously or sequentially to the hair keratin fibers.