Most of our print drivers have the ability to restrict color printing.
Make sure this option isn't selected in printer properties. See image below.
You can also use the Defaults button to set that settings tab back to defaults
The serial number is 9 characters beginning with YXE in the US regions.
Where are you located?
What driver version are you using? You can check the driver version by going to printing preferences/advanced and selecting the about button.
How is the printer connected USB or Network? Sometimes print queues become corrupt and can get stuck in black and white only mode. Have you tried deleting the printer, rebooting and then reinstalling? Have you tried resetting the defaults for each tab in both printer properties and printing preferences?
If the product is still under warrantee I would recommend calling in for a quicker resolution.