Method for determining parameters specific to the custom-made coloring of the hairs of a given individual

A method for determining at least one parameter specific to the custom-made coloring of hairs of a given individual, according to a colorimetric rendering model, the method comprising an initialization phase corresponding to a first coloring of the hairs of the individual, the initialization phase comprising the steps of:

• receiving at least one magnitude representative of a first target color in a colorimetric space,
• receiving at least one magnitude representative of a first initial color in the colorimetric space, the first color being the color of the hairs to be colored of the individual,
• determining a cosmetic product composition according to the magnitudes representative of the first initial color and of the first target color and of the colorimetric rendering model,
• applying a cosmetic product having the determined composition on the hairs to be colored of the individual in order to obtain colored hairs,
• evaluating the color of the colored hairs in order to obtain at least one magnitude representative of a first final color in the colorimetric space, and
• determining at least one colorimetric deviation parameter specific to the individual according to the magnitudes representative of the first final color and of the first target color.