A coating composition includes, in relation to 100% of the weight thereof: between 10 and 90 wt. % of at least one film-forming polymer selected from cellulosic polymers or derivatives of cellulosic polymers, derivatives of vinyl alcohol, derivatives of vinyl pyrrolidones, polymers of a natural origin, acrylic or methacrylic derivatives, derivatives of glycol or propylene glycol or combinations of the two substances or the copolymers of vinyl alcohol and polyethylene glycol (PEG); between 1 and 50 wt. % of at least one food colouring agent; and between 0 and 50 wt. % of at least one auxiliary coating agent selected from white opacifiers, diluents, surfactants, plasticizers, and anti-foaming agents.