1. An image forming apparatus that forms a color image, comprising: determination means for determining whether image data of an object to be drawn is composed of gray data and a color value of the object is greater than a determination value; erase means for erasing, if the determination means determines that the image data of the object to be drawn is composed of gray data and the color value of the object is greater than the determination value, image data of a background region that overlaps a drawing region of the to-be-drawn gray object on the basis of a preselected erasure pattern; and drawing means for drawing the gray object using the image data of the background region that is erased by the erase means.