1. A control device for controlling a printer comprising: a print head having a plurality of sets of nozzles, each of the plurality of sets of nozzles being configured to eject ink in one of a plurality of colors, the control device comprising: a controller configured to perform: acquiring target image data representing a target image, the target image including a first image within a first region and a second image within a second region; calculating an index value indicative of an amount of a specific type of ink in a specific type of color to be used in printing at least a part of the target image; determining whether the index value is greater than a threshold value; in response to determining that the index value is not greater than the threshold value, controlling the printer to perform a first process to print the first image and the second mage using the specific type of ink but not using a different type of ink different from the specific type of ink for reproducing the specific type of color; and in response to determining that the index value is greater than the threshold value, controlling the printer to perform a second process to print the first image using the specific type of ink but not using the different type of ink for reproducing the specific type of color and to print the second image using the different type of ink for reproducing the specific type of color.