Magnesium oxide is typically white and can be colorized with transition metal insertion by doping or by adsorption. We present the preparation of green colored hydroxide by the adsorption of nickel ions by porous MgO. MgO was prepared by the colloidal starch suspension method and used to remove nickel ions from the aqueous solution. The oxides and hydroxides, before and after adsorption, were characterized by X-ray diffraction technical, and show that a phase change occurs, a transition from periclase (MgO) to brucite (Mg(OH)2) due to the interaction with nickel salts (acetate, chloride, and nitrate). The FTIR spectrum corroborates with the DRX data on the formation of brucite like crystal lattices. The new samples present a green color, indicative of the incor-po-ration of the Ni2+ ions. Mixed oxides in the form of brucite were used in microbiological tests and showed action against fungi and bacteria, with bactericidal, bacteriostatic, or fungistatic function. Green brucite (NixMg1-x(OH)2) can be used as an inorganic pigment in white or colorless paints with a special biocidal property.