1. An image forming apparatus comprising: a color matching unit to match colors of a color document containing one or more images comprising a preset number of colors with colors available in the image forming apparatus; a color table generator to generate a color table using the matched colors; a compared color extracting unit to compare colors extracted from a scanned color document with colors in the color table, and to determine output colors in the images when a correlation between the extracted colors from the scanned color document and colors in the color table is equal to or less than a predetermined threshold; and an output unit to print the color document using the determined output colors available in the image forming apparatus, wherein the preset number of colors of the color document are determined according to whether the color document corresponds to a predetermined document type.