If you don't want to replace the color cartridges, you can fool the printer instead. Sensors in the printer shine light through a thin area on the cartridges. The empty (or even just low, even though there may be plenty of ink still inside) cartridges allow the light to get through, the printer sees the empty cartridges, and it won't print anymore. You can cover this part of the cartridge with a piece of black electrical tape to block the light. Voila! No light gets through and the printer thinks you have full cartridges again. This site
has pictures showing where to put the tape. I've used this trick on the printer we have here in our office and it works great.