Each cartridge for the HP 2550 requires a separate chip.  Each color chip (for example, the black chip) works only specifically for that color cartridge and does not work in the other color cartridges. Please also note that while the HP 2500 and 2550 cartridges use the same toner and drums, the smartchips are different and you can not use a HP 2500 chip in a HP 2550.