Why does color ink in Photosmart C7280 go down when you are only printing using black ink

Sadly not. The HP Photosmart C7280 insists on having a full set of cartridges installed in order to print. It does this because the printheads are actually part of the printer itself and can sustain damage if they pull air into the printhead.

The out of date message is also non-negotiable I am sad to say.

You can't

you need to make sure all your ink cartridges are full, if they are, I would take them out and put them back in and rerun alignment

1. Unplug power cable while the printer is ON.
2. Press and hold the '#' and '3' buttons, and plug the cable back into the printer.
3. Continue holding the buttons down for 20 seconds, and then release it.

if doesn't initialize successfully repeat
on step 2 press and hold the '#' and '6' button and plug in the power cable.

Try holding down the ok -- cancel -- black -- color buttons with 4 fingers while at the same time powering the unit off. Keep them held down till it is off. Then turn it back on normally & it should try to do "Maintenance" & you hear a whirling noise --- that is the ink pump spinning to try & pump in ink to the print head.
You may also try this: Press and hold the '*' key on the key pad, then press the '#' key and release them both. Then enter '123' to enter maintenance mode. Then press the right arrow (beside the OK button) until System Config. menu appeared on panel. Then press OK two times to clear the error condition, then cancel two or three times to return to the top menu. Then power it off and back on.

Hi there
Yes you need all inks to be working or printer not work

Does the c7280 use seperate Magenta and PhotoMagenta cartridges? If so make certain the right cartridge is in the correct slot.

Something is wrong with your Blach carrier or connections. Use a bit of alcohol and clean the array of gold contacts where the Ink cartridge plugs in. Most of the pins are shutter and piezo control (get the ink on paper) but a few do other stuff like check ink level, # of hours runtime, etc. This is very common problem with inkjet printers. Hope this helps.
Also... rub the contacts on the printhead with a pencil eraser to make them shiny and bright.

Cheers!

Why don't you try changing the Setup for your printing to Black & White or Grayscale in your computer's software: File/Print/go to the printer's settings and disable anything color. As for the cartridge, it's probably the cartridge. If you have an extra, why not swap it out? I believe the brains in the cartridge contacts might not be working properly OR your heads need to be cleaned OR you better stick with HP original cartridge to make sure it's not the printer. I used to use "odd" ink and even refilled ones and shortly thereafter my old printers would die. Not taking a chance on this HP. I love how it prints when it isn't jamming the paper! Need help on that problem pronto.