Devices, methods and techniques related to image rendering for ground-penetrating radar (GPR) systems are disclosed. In one example aspect, a method for producing one or more images associated with a GPR includes receiving information representative of signals received by the GPR, determining at least three frequency bands associated with the received information, assigning color values to the received information corresponding to the at least three frequency bands, and generating a color image for the one or more objects by combining the received information in all of the at least three frequency bands together such that the color values in the color image indicate a size of the one or more objects, a depth at which the one or more objects is buried underground, or an electrical permittivity of the one or more objects.