I had been doing Tech Support for Hewlett-Packard's DeskJet division for about a month when a customer called with a problem I just couldn't solve. She could not print yellow. All other colors printed fine, which truly baffled me because the primary ink colors are cyan, magenta, and yellow.
I had the customer change ink cartridges, delete and reinstall the drivers. Nothing worked. I asked my coworkers for help, but they had no new ideas.
After over two hours of troubleshooting, I was about to tell her to send the printer in for repair when she asked quietly, "Should I try printing on a piece of white paper instead of yellow paper?"