A display includes a display unit, an image sensor that takes an image of a predetermined area and outputs the taken image, and a hardware processor that detects the marker in the taken image, generates differential color information between color data of the marker in the taken image and color data of the marker in the print image data, displays a virtual object which reproduces the print image data in the display unit, sets an object adjustment value for adjusting a color tone of the virtual object displayed on the display unit based on the differential color information, and calculates a print adjustment value for adjusting a color tone reproduced by the image forming apparatus based on the object adjustment value.