Abstract: A method of processing diamond particles to form fluorescent color centers involves providing diamond particles containing at least one dopant; annealing the diamond particles in a vacuum or an inert atmosphere; creating vacancies in the annealed diamond particles by irradiating the diamond particles with high energy radiation; and while the annealed diamond particles are being irradiated, causing a temperature of the diamond particles to be at least a temperature at which vacancies in the diamond particles diffuse and combine with the at least one dopant to form fluorescent color centers. The procedure can be repeated at least twice. This abstract is not to be considered limiting, since other embodiments may deviate from the features described in this abstract.