The present invention relates to a composition for dyeing and/or lightening keratin fibres, in particular human keratin fibres such as the hair, comprising: a) one or more guanidine salts, b) one or more alkanolamines, c) ammonium hydroxide and d) at least two polymers chosen from cationic and amphoteric polymers, which are different from each other, e) optionally one or more colouring agents. The invention also relates to a dyeing and/or lightening process using said composition, and also to a multi-compartment device which is suitable for using said dyeing and/or lightening composition.
