Thank you, Laurens73
I followed your advice and killed all processes related to audio/video/mixers, but the green Volume and bars didn't go away. Then I logged out and back in as Administrator, because I NEVER used any audio applications in an Administrator session. The green Volume showed up on the Administrator desktop background too !! That made me realize that the problem must be a hardware issue, not a running application process issue. Then I removed the USB external speaker, and finally the screen display went away. After some time, I was able to change the volume controls on the external speaker, and the green Volume display did not return, even when the speaker was re-attached.
Thanks to YOU, I learned about using "top" at the command line, and I was able to get to a solution for the problem.
Now a new issue has arrived. The external speaker can be selected from my SKYPE options, and it works perfectly. I cannot find out how to make the USB speaker the DEFAULT audio for all applications. Control Center, Hardware Detection identifies the external speaker as a "Generic Device" instead of an "Audio Device". I am trying to learn now how to make the USB device become the default audio device for use with the ALSA controller.
Best regards, sladel (who has fond memories of travel in Holland)