GRD is an extension given to files associated with the Adobe Photoshop professional graphics editor. GRD files are used to store gradient fill patterns with which you can fill specific areas of images edited in the program. These are most often multicolored patterns in which the colors usually change in a smooth (gradually) manner. Sometimes the so-called tonal transition, ie transition from a darker shade of color to its "fading".

Adobe Photoshop is a tool for Windows and Mac.