In case anyone is interested, the problem is solved. I guess I just was not paying close enough attention. Apparently, if you just click on "Print", the machine uses a combination of colored and black ink to create a black letter. I bought a combo pak of black and tricolor cartridges but, thinking only the black was out, replaced only that one. I tried to make sure it would print in black by, when what I think is called the print dialog box came up, clicking on "Preferences" and then clicking on "Print in Grayscale".
I didn't realize at the time, that I had to take it one step further. When I put the checkmark in "Grayscale", the dots under the check lit up. The default setting is, "High Quality", and I should have clicked on, "Black Only".
Apparently the red ink, in the color cartridge, also out, leaving blue and yellow, which made green and, combined with some black, made dark green.
I have now replaced the color cartridge, along with the black, and the problem is taken care of.