This method for determining a skin colour of a region of interest of a user, comprises: —importing, from an image library (LIB) of a user computational device (APP), at least one image (IMk) comprising a representation of the region of interest of the user; —performing processing (TS) of said at least one image (IMk) with a machine-learning model (AI_TS) suitable for providing, for each imported image (IMk), a numerical value (ClrEstm_k) representative of the skin colour of the region of interest present in said at least None imported image (IMk); —performing evaluation (EVAL) of the skin colour of the region of interest on the basis of said one or more numerical values (ClrEstm_k) of each imported image.