A method for preparing an agent for changing the color of keratin fibers, in particular human hair, which comprises unilamellar vesicles and/or multilamellar vesicles in an aqueous medium, the agent containing at least one C 8 -C 30 fatty alcohol at least one ethoxylated fatty alcohol of formula where R1 represents a linear or branched, saturated or unsaturated C 8 -C 30 alkyl group and n represents an integer from 10 to 100, at least one anionic surfactant of formula where R2 represents a linear or branched, saturated or unsaturated C 8 -C 30 alkyl group, m represents an integer from 0 to 10 and M represents a hydrogen atom, an equivalent of a sodium ion, potassium ion or ammonium ion (NH4 +), and one or more color-changing salts from the group of sulfates, hydrogen sulfates, chlorides and/or bromides in a total amount of 0.9 to 3.4 wt.%, the total amount being based on the total weight of the agent, characterized in that the method comprises the following steps heating a mixture consisting of C 12 -C 30 fatty alcohol, ethoxylated fatty alcohol of formula, anionic surfactant of formula and a first partial amount of water to a temperature of 65 to 85 °C in a first container, preparing a mixture consisting of a second partial amount of water and the color-changing salts from the group of sulfates, hydrogen sulfates and chlorides in a second container, adding the preparation obtained in step to the preparation obtained in step and temperature-controlled to 40 to 60 °C, with constant stirring using a propeller agitator at at least 500 revolutions per minute, cooling the mixture obtained in step to 20 to 40 °C with constant stirring. at least one C 8 -C 30 fatty alcohol at least one ethoxylated fatty alcohol of formula where R1 represents a linear or branched, saturated or unsaturated C 8 -C 30 alkyl group and n represents an integer from 10 to 100, R1 represents a linear or branched, saturated or unsaturated C 8 -C 30 alkyl group and n represents an integer from 10 to 100, at least one anionic surfactant of formula where R2 represents a linear or branched, saturated or unsaturated C 8 -C 30 alkyl group, m represents an integer from 0 to 10 and M represents a hydrogen atom, an equivalent of a sodium ion, potassium ion or ammonium ion (NH4 +), and R2 represents a linear or branched, saturated or unsaturated C 8 -C 30 alkyl group, m represents an integer from 0 to 10 and M represents a hydrogen atom, an equivalent of a sodium ion, potassium ion or ammonium ion (NH4 +), and one or more color-changing salts from the group of sulfates, hydrogen sulfates, chlorides and/or bromides in a total amount of 0.9 to 3.4 wt.%, the total amount being based on the total weight of the agent, characterized in that the method comprises the following steps heating a mixture consisting of C 12 -C 30 fatty alcohol, ethoxylated fatty alcohol of formula, anionic surfactant of formula and a first partial amount of water to a temperature of 65 to 85 °C in a first container, preparing a mixture consisting of a second partial amount of water and the color-changing salts from the group of sulfates, hydrogen sulfates and chlorides in a second container, adding the preparation obtained in step to the preparation obtained in step and temperature-controlled to 40 to 60 °C, with constant stirring using a propeller agitator at at least 500 revolutions per minute, cooling the mixture obtained in step to 20 to 40 °C with constant stirring. heating a mixture consisting of C 12 -C 30 fatty alcohol, ethoxylated fatty alcohol of formula, anionic surfactant of formula and a first partial amount of water to a temperature of 65 to 85 °C in a first container, preparing a mixture consisting of a second partial amount of water and the color-changing salts from the group of sulfates, hydrogen sulfates and chlorides in a second container, adding the preparation obtained in step to the preparation obtained in step and temperature-controlled to 40 to 60 °C, with constant stirring using a propeller agitator at at least 500 revolutions per minute, cooling the mixture obtained in step to 20 to 40 °C with constant stirring.