My c353 konoca Minolta is showing p7, p8, p21 and it print test page with black and cyan only.

SOURCE: Yellow Prints in the other colors

Problem seems to be with your Ink Tank(s) or Printing Head. Replace both of them one by one and retry.

SOURCE: Light or Faded Areas in Solid Color Prints

If the issue is occuring in the same place on all prints, try the imaging drum (can't remember if this printer even uses one) or the transfer belt/roller (not sure which it uses). If you phone Dell support, they should run you through troubleshooting and send you either of those parts free of charge if you are under warranty. If not, buy them anyways; they don't degrade over time (if kept in the dark) and can be saved for when the currently installed one runs out if you don't need it to fix this issue.

SOURCE: INK DEPLETED BLOCKING ALL FUNCTION

Both of the cartridges did need replacing; the black is OK now so just pop in a cyan and you should be fine.

SOURCE: Xerox Phaser 8560 Color not correct

the problem is not with the printer but it is with the ink that might be damaged, this is located inside the printer

SOURCE: Brother MFC 5860cn magenta color is not printing

This can happen if the ink dries out for a long time. Try to power flush the color that doesn't work.

Press the Menu/Set, *, 2, 8, 6 and 4 keys within two seconds. (if you fail to complete the correct key sequence within two seconds, press the Stop key to try again).

press 7 then 6 then 4 then start black copy. This will fill the tubes with ink.

press 7 then 6 then 3 then start black copy. You may use the right arrow to choose the color you want to flush before you press the black copy button.

Press 99 to exit maintenance mode

Press the ink button and do a test print for print quality and see if the color you flushed works. If not, try again.

This is the only way to fix the dried print head. Otherwise you have to replace the print head, in which case, you might as well buy a new printer.