A multi-color projection scheme based on single grating light modulator (GLM) using three-color lasers as light source is proposed. First,the principle of color display is explained. Second,red,green and blue laser composing standard D65 white light source is analyzed by colorimetry theory,considering three important indicators,displaying reduction degree of color,displaying brightness and output power of laser. The laser light source is analyzed and optimized. The result indicates that the combination of the lasers with wavelengths of 635,532 and 457 nm is the best optimal project. The experiment system is set up,and the color projection experiment based on static grating light modulators is carried out by collecting the ±1st order diffraction light. Red,green,blue and white projection pattern is obtained through the experiment,which preliminarily proves the validity of this color projection scheme.