I think I have found a solution: The problem seems to be the spring on the component shown here:
I removed the spring (as shown in the video), I pulled a few times, and I put it back. And now the printer can print also in color. I did a few prints, and it seems to work.
Is there a "replacement" spring?
I am facing the exact same problem. My 6121 MFP can print its menu/configuration pages (which are black and white), but it cannot print the demo page, which is in color.
It always ends with the same error (papaer jam in fuser), and I have to open the top cover and remove the half-printed color page...
My printer reports that I have printed 3757 pages in total.
Also, I am located in Greece.
Sounds like it would be time to change your fuser but if you haven't received the message to change it, I would recommend contacting the Support Department: 1-800-821-2797
Xerox Phaser 6121 Mfp Prints Fine In B&w But Jams In Fuser When Printing Colour.
Each time I try to print anything in colour on my printer it jams and reports the jam to be in the fuser.
When I try to print in black and white however, it prints with no problems at all. No error codes.
Any suggestions as to how to fix this?