A method for generating an x-ray image in color includes selecting three-sets of x-ray images in gray scale acquired with x-rays having different energy spectra, assigning basic colors RGB to the three-sets, and displaying the x-ray image in color with RGB signals generated. A system for generating an x-ray image in color includes an x-ray generator configured to generate at least three sets of x-rays with different energy spectra, an x-ray detector, a controller, a computer, and a color display. The computer is configured to generate three sets of x-ray images from output data of the x-ray detector acquired for x-rays with different energy spectra, assign RGB and display an x-ray image in color. A non-transitory computer readable medium stores an instruction, when the instruction is executed by a processor, cause the processor to perform the method for generating an x-ray image in color.