Open Terminal and run:

cupsctl WebInterface=yes

Open Safari and go to: http://localhost:631/printers. Here you can click on the printer name and see more specifications such as the IP address used.

Open Terminal and run:

cupsctl WebInterface=no

(Thanks to some useful tips at http://apple.stackexchange.com/questions/198037/how-do-i-get-the-actual-ip-address-of-a-printer-in-osx-yosemite)