Hi jodo41,
I understand you have an Officejet 8500 A909a that is not printing in color from your Mac. I'm sorry to hear this, but I will definitely do my best to assist you.
When you installed the software on your Mac, did you remove any previous HP software and then install the 8500 following this OS X v10.9 Mavericks: Installing and Using the Printer on a Mac document? If not, you will need to follow this Uninstalling the Printer Software document to remove the software and then follow the previous document to install the printer via the Apple Updates.
Once that is done you should be able to print in color or black, whichever you'd prefer.
Hope this helps, have a great day!!