Dispersibility of zinc nanometer-sized particles dispersed in several organic liquids is described as a function of ESR g shift. When a colloid is in dispersion, the g value coincides with that of isolated particles, in contrast to the case of aggregation, where the g value shifts toward that of bulk metal. The g values of zinc nanoparticles in several liquids as a function of the dielectric constant of liquids are classified along with the dispersibility of colloids. Since the g value reflects the electronic state of metals, the stability of the colloidal system is represented in terms of the electronic state of metallic particles.