On every page printed or just when you print the test page? I.e., you write first "on all copies" and then secondly "On a printer test page....."
I would expect that line of colors on a test page and I doubt you would have posted if the problem was not appearing on all pages.
Do you have the user manual? Does the color pattern match any of the patterns used for the printer's test page?
Can you make the color line move by changing page margins, headers, etc..