A non-transitory computer-readable medium stores computer-readable instructions for sewing data generation executed by a processor in a sewing data generation device. The instructions comprises acquiring image data and determining a mode to determine a tendency of a plurality of thread colors to be used. The plurality of thread colors to be used is thread colors used in sewing of an embroidery pattern that represents an image represented by the acquired image data. The instructions also comprises selecting, on the basis of a target mode that is the determined mode, a plurality of thread colors among which at least one thread color is different for each of the modes, from a plurality of thread colors stored in a storage portion, as the plurality of thread colors to be used, and generating embroidery data to form, using a sewing machine, stitches of the selected plurality of thread colors to be used.