I just put new color ink in my printer,but only the blue shows why??

If the cartridge is old, the red and yellow color jets may be clogged. Get a coffe cup, about half an inch of water and heat it in the microwave until steaming. Remove cup from microwave and place the print cartridge in it jets down. In about 30 seconds you should be able to remove the cartridge and dab it with a paper towel and see all the colors coming out. Once dry, replace into your printer.