1. A non-transitory computer-readable medium storing computer-readable instructions, the instructions, when executed by a processor of an image processing apparatus, performing processes comprising: registering, in a storage, a candidate color for each of a plurality of divided areas included in image data indicating an image on a sheet, the candidate color being a color value of a representative color representing color values of a plurality of pixels included in the divided area; determining whether a first color distance is less than a first threshold value, the first color distance being a distance in a three-dimensional color space between a color value of a target pixel and a white reference value corresponding to a color value of white, the target pixel being one of the plurality of pixels included in the image data; determining whether a color value of a target color is further separated from the white reference value than the color value of the target pixel in the three-dimensional color space, the target color being the candidate color closest to the color value of the target pixel among the plurality of candidate colors registered in the storage; and replacing, when it is determined that the first color distance is not less than the first threshold value or when it is determined that the color value of the target color is not further separated from the white reference value than the color value of the target pixel, the color value of the target pixel with the target color, without replacing the color value of the target pixel when it is determined that the first color distance is less than the first threshold value and it is determined that the color value of the target color is further separated from the white reference value than the color value of the target pixel.