The present invention relates to a dye composition comprising: * at least one oxidation dye precursor； * at least one polycondensate of ethylene oxide and of propylene oxide having the structure (A) below H&mdash；(O&mdash；CH2&mdash；CH2)n&mdash；(O&mdash；CH(CH3)&mdash；CH2)b&mdash；(O&mdash；CH2&mdash；CH2)a&mdash；OH (A) in which formula a and a&prime； range from 2 to 150 and b ranges from 1 to 100； and * at least one C8-C30 fatty alcohol comprising at least one unsaturation. The invention also relates to a dyeing process using this composition (free of oxidizing agent) after mixing with a composition comprising an oxidizing agent. Another subject of the invention is a two-compartment device, the first compartment comprising the composition according to the invention, free of oxidizing agent, and the second compartment containing a composition comprising at least one oxidizing agent.
