Abstract: The invention relates to a dye composition, in particular a lightening dye composition, for keratin fibers, in particular for human keratin fibers such as the hair, comprising, in a medium which is suitable for dyeing, at least one direct dye to be mixed at the time of use, at basic pH, with an oxidizing agent, and characterized in that it has a basic pH and in that it contains, as direct dye, at least one dye containing an optionally delocalizable quaternized nitrogen atom and a —Z═N— bond in which Z denotes a nitrogen atom or a —CH— radical.