Phiwie,
Sensor in both catridges, so both need some ink to print. You can tell it to use Black only, in printer preferences.
Can you copy a document under the glass? Black & white and color? If not, the problem is the printer, either the Dell Series ink cartridge(s) or the printhead. I have see a few of the print heads go out, the original failed at an early time, but the replacement printhead has made mine last for years.
Rick