HP 2000CP 2500CP - Manual (Page 154)

6-12 Image Quality HP DesignJet CP Series Printers
Banding Problem 6: Different colors visible in the spaces between
some or all of the columns (depending on the color
of the printhead that is misaligned) (see Example
C).
Problem Description: This is an indication of vertical misalignment.
Corrective Action: Refer to Test Pattern 4
' page 6-14 to
troubleshoot the problem.
It is also possible that the banding was caused because the customer
was using non-HP media. The performance of the printer can only be
guaranteed if genuine HP media is used.
Example C