The changes in the fluorescence color can be well explained by formation and annealing of NV and H3 luminescence centers, which are common contributors to the fluorescence of nitrogen-containing diamonds. Strengthening of the green color component is the result of the increase in intensity of H3 centers. The red-pink color is the manifestation of the formation of NV centers. The yellow-orange component in strong green fluorescence is frequently caused by emission of NV” center.