I'm having the same problem with a C8055. All simplex scans through the doc feeder are all yellow...and after being on the phone with Level 2, the blue values were super low.
I have replaced the ribbon cable and the IIT PWB and it's STILL doing it. Alt boots did nothing.
Whenever we try to make colored copies with the feeder tray, the whole page turns yellow.
It does not do this if we try to make colored copies with the scanner, or black and white copies through the feeder. I have reset the system, reset the settings, made sure background suppersion in on.