Thanks for all the help guys.
I figured it out, but not sure how to fix it. In my Nvidia panel, I choose "Adjust Desktop Color Settings". Under Option 2, "Choose how color is set", I choose "Use NVIDIA settings", then I have my custom values for each setting such as Brightness, Contrast, Gamma, etc. The backglass monitor displays images using my custom color settings fine except when PinballX is loaded during attract mode. Once a table is launched, the backglass monitor displays the custom color settings correctly. I tried running a bunch of other apps and they all show the custom color settings correctly. I tried turning off Option 2, "Choose how color is set" and switching to "Other applications control color settings". The backglass during Pinballx attract mode shows the same color representation now as when the table is loaded - I just don't like how the color looks and prefer to use the NVIDIA settings as the color pops much more.
I also updated to 3.43, the resolution of the video and the monitor is HD 1080x1920 and I recorded all the videos myself using the PBXRecorder. I also tried switching a table video with the backglass video and same issue.