I fumbled around with it for a while, gave up and went to bed, and this morning in desperation I deleted all printers from the system and used the "Add Printer" wizard in Windows 10 to reinstall it.

The first time, I told it to use the existing driver, the printer installed and printed black and white only.

I deleted the printer, did the reinstall thing and told it to use a different driver. The printer installed, and now prints in color.

I don't know where the "different" driver came from, I think it is the same PCL-6 driver I have always used. It didn't take long enough for the computer to have downloaded a new driver from somewhere, so does Windows 10 have a reservoir of drivers built in that it installs as needed?

At a guess (reinforced by invincible ignorance) whatever wiped the configuration settings from my router also corrupted the print driver. At least everything is working. For now, anyway...

My printer can connect via USB as well as through the Ethernet network. Can I install it both ways, so I can select which way I want to print?

tanstaafl.