The present invention relates in general terms to an antimicrobial composition having chlorhexidine and a dye selected from 3,7-bis(dimethylamino)-phenothiazin-5-ium chloride and a sodium or calcium salt of [4-(α-(4-diethylaminophenyl)-5-hydroxy-2, 4-disulfophenylmethylidene)-2,5-cyclohexadien-1-ylidene] diethylammonium hydroxide usable in the medical field. In particular, the invention relates to the composition in the form of aqueous solution, hydro-alcoholic solution or gel, and its use as a coloring antiseptic and disinfectant agent, for example in pre-surgical procedures.