Found the cause of external display problems when using 2018 Mac mini with HDMI

I recently bought a new 2018 Mac mini, to replace an older, but still usable, 2014 Mac mini. The old Mac used Mini DisplayPort to connect to an external monitor. I used that instead of HDMI because the older Mac could not get higher resolution using HDMI v1. The new Mac does not use Mini DisplayPort, so I planned on using its HDMI v2 port to connect to the monitor. This seemed to work at first, but I noticed my screen would turn to greyscale seemingly at random. (see image I snapped with my phone while playing Civ V). It didn't matter if I was using a browser, the App Store, a full-screen game, or just nothing open at all. I finally found the cause for this. The monitor, in this case an Acer K272HUL, had an OSD setting for "Detect Video" it was set to "on". Before, when I was using the Mini DisplayPort, there was no problem. Out of curiosity, I changed this setting to "off". (see second image). The greyscale effect immediately stopped and has not returned. I thought the issue might have been a problem with the Mac, or possibly the cable, or even the monitor, but it turns out it was just this monitor setting. I'm posting this in hopes that it might help someone else who might be experiencing the same issue.