Hello fenwayfan and Welcome to the HP Support Forums!
I understand that the only color that works is green with your PSC 2170 All-in-One. I can provide you a handy document that may be able to resolve this issue.
Here it is: Correcting Printing Quality Problems When Printing from Windows
If all steps in the document do not provide a solution, please contact HP support for repair or replacement
options available for you.
HP support phone contact is 1-800-474-6836.
If you live outside the US/Canada Region, please click the link below to get the support number for your region.
http://www.hp.com/cgi-bin/hpsupport/index.pl
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