X 3 MgSi 2 O 8 : Eu 2+ , Mn 2+ (X=Ba, Sr, Ca) phosphors with the mean particle size of 200nm and the spherical shape are synthesized through combustion method. They show three emission colors under near-ultraviolet light: the blue and green colors from Eu 2+ ions and the red color from Mn 2+ ions. Three emission bands show the different emission colors with changing X 2+ cations. These color shifts are discussed in terms of two competing factors of the crystal field strength and the covalency. These phosphors with maximum excitation of around 375nm can be applied as color-tunable phosphors for white-light-emitting diode based on ultraviolet/phosphor technology.