Your Brother machine is designed to stop ALL printing operations when any of the ink cartridges are empty. This is to ensure the life of the print head and maintain premium print quality. If the unit were to continue printing, print jobs and cleaning cycles would suck air from the empty cartridge and damage the print head. Even if you print in black only or change the print settings to "Mono" or "Grayscale" to avoid printing in color, the programmed cleaning cycles would still suck air from the empty cartridge, because they are programmed to clean ALL the ink nozzles. The only way to continue printing is to replace the empty ink cartridge(s).