1. An image forming apparatus comprising: an image reading device that reads an image of a record sheet including a region of a fluorescent color applied by a fluorescent pen, reads an image of a document sheet, and generates image data of the read images; a printing device; a fluorescent color recording portion that reads a color value of the fluorescent color in the record sheet, causes the printing device to print a group of neighboring color patches that includes a plurality of color patches representing the read color value and color values neighboring the read color value, identifies a color patch selected by a user from among the group of neighboring color patches having been printed, and records a color value of the color patch in a color coordinate system of the printing device, and the color value of the fluorescent color so as to be associated with each other; and a color conversion portion that generates, when the fluorescent color is not included in the image of the document sheet, image data according to the color coordinate system of the printing device for the image of the document sheet, in a predetermined color conversion mode, based on the image data of the read image, and, when the fluorescent color is included in the image of the document sheet, generates, for colors other than the fluorescent color, image data according to the color coordinate system of the printing device for the image of the document sheet, in the predetermined color conversion mode, based on the image data of the read image, and generates, for the fluorescent color, image data according to the color coordinate system of the printing device for the image of the document sheet, based on the image data of the read image, by using the color value of the color patch corresponding to the recorded fluorescent color.