1. An image processing apparatus, comprising: an operation device configured to receive a user instruction input by a user, the operation device simultaneously displaying a plurality of image processing functions to be applied onto image data by the image processing apparatus, the user instruction indicating a selection of at least one of the functions; a document type detector configured to determine whether the image data is in color or monochrome; a color vision type detector configured to automatically determine a color vision type of the user who inputs the user instruction based on the user instruction; and a color converting device configured to, when the image data is determined to be in color, detect a section in the image data that includes a pseudoisochromatic color that can be hardly recognized by the user who inputs the user instruction and is assumed to have the determined color vision type, and to convert the pseudoisochromatic color of the detected section to a color that can be easily recognized by the user who inputs the user instruction and is assumed to have the determined color vision type to generate processed image data.