I was a Mac Genius in the HP iPod era. When Carly Fiorina introduced the HP iPod she said that it would come in “HP blue”. But, in fact, it only ever came in white. The only way to tell if a 4th Generation iPod was an HP, and not Apple vended, was “HP" was inscribed on the back. There were also HP iPod minis, which only ever came in silver. The internet tells me there were HP also sold co-branded iPod shuffles, I don't remember ever seeing one, though.
People would bring HP iPods to the Genius Bar, but we did not service them as HP had agreed to take on the responsibility for that. This seemed to confuse a lot of people.