I finally found the explanation of the complex HP printer color test
pages!

So that others save the time it took me to find this explanation of the
intricate color test patterns output by an HP all in one officejet
printer, see the explanations at:
http://h10025.www1.hp.com/ewfrf/wc/f...me=bpa0022 4#

>From the color test results, I'm assuming the HPC4921A #14 CYAN print
head is clogged. Since the print head is no good, I just now soaded the
top screen in amonia and gently wiped the bottom gold contacts with an
alcohol soaked cotton swab. This didn't seem to unclog the print head
so I am still looking for a better way to clean the printhead than this
procedure (which I found by googling).

Susan