Hello Harvey, unfortunately your file does not work... but in the meantime I found an old beta version and I did some tests on a virtual machine. And finally, after many, many attempts, I found a way to change the backgrounds of Explorer and applications!!! For those who are interested the items to change are:

1) Fonts, Colors, & System Metrics -> Fonts & System Metrics = WINDOW:COLOR (change the color of the application's work area).

2) Explorer & Shell -> Explorer -> Items View -> ItemsView = FILLCOLOR:COLOR (change the color of the right side of Explorer).

3) Explorer & Shell -> Explorer -> ProperTree -> Background = FILLCOLOR:COLOR (change the color of the left side of Explorer).

For those who want to create various styles with different backgrounds, I recommend creating a folder for each style (aero2, aero3, aero4, etc ...).

Thanks for the support and good customization to all of you!!!