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 from about 50% to about 80% by weight of a fatty substance comprising a viscosity greater than about 50 mm2/s at 40° C. and optionally, an additional fatty substance a rheology modifying polymer an alkalizing agent a short alkyl chain hydroxy compound chosen from monoalcohols and polyols an oxidative dye precursor and an oxidizing composition comprising an oxidizing agent and wherein the pH of the agent for altering the color of keratin fibers ranges from about 1 to about 7.
