In Cinnamon Settings under Themes, changing "Cinnamon theme" doesn't affect the appearance of your windows or icons, they are shell themes only. Go into "Other settings" and choose a new icon set. The "Gnome" option has grey folders if that's what you seek.
Thank you for this thread. That’s all I can say. You most definitely have made this forum into something special. You clearly know what you are doing, you’ve covered so many bases. Thanks!