An image forming apparatus includes an image data acquisition unit, a frequency distribution acquisition unit, and a color setting unit. The image data acquisition unit acquires image data representing a color image. The frequency distribution acquisition unit allocates a color of each pixel of the data as a class and acquires a frequency distribution representing an occurrence rate of the color based on the data acquired by the image data acquisition unit. The color setting unit sets a first color with the highest frequency distribution occurrence rate as a background color in the color image, sets a second color with an occurrence rate next in magnitude to the first color as a character color in the color image, and sets a color with an occurrence rate lower than that of the second color as a pattern color that is a color of a specific pattern in the color image.