The present invention is drawn to an agent and process for altering the color of keratin fibers wherein the agent comprises: (A) a color base composition containing a fatty substance having a viscosity greater than about 50 mm2/s at 40°C a rheology modifying polymer and an alkalizing agent a short alkyl chain hydroxy compound chosen from monoalcohols and polyols a direct dye and optionally an oxidative dye precursor and (B) optionally, an oxidizing composition comprising an oxidizing agent.