1. THE PROCESS OF COLORING SUBSTANTIALLY COLORLESS DIAMONDS COMPRISED OF THE STEPS OF SUBJECTING THE COLORLESS DIAMONDS TO IRRADIATION BY ELECTRONS HAVING AN ENERGY OF 1 MEV. FOR APPROXIMATELY 1 HOUR HAVING AN INTEGRATED ELECTRON FLUX OF BETWEEN 1 AND 2X10**18 ELECTRONS/CM.2, WHEREBY THE DIAMONDS TAKE ON A BLUE COLOR WITH A SLIGHT GREEN TINT, AND THEN HEATING THE IRRADIATED DIAMONDS AT 500*C. FOR HALF AN HOUR WHEREBY THEY BECOME PURE BLUE.