How can I assign different `TAB only` colors.. to specific drive letters?

I would like to assign, for example.. a RED color to my C: drive TAB (tab only). I also want the C: drive tab to always stay RED, regardless of which side of the dual-pane I am in within the lister.. and regardless of which sub-folder I am in. I visually want to know when I`m in the C: drive by the color of the tab I assign globally. Hope this made sense..

Had this working flawlessly on another computer years ago, but I no longer recall how it was done and cannot find the answer on this forum. Any help would be appreciated..

In Opus 13, you can configure that via Preferences / Folder Tabs / Edge Colors.

In Opus 12, it was part of Folder Formats (on the Options tab of the format, if I remember correctly).

Oddly enough, this post of yours from elsewhere in the forum had me hover over the lock.. only to realize it was locked! BOOM! Once I unlocked it, any changes I made in Folder Options or Folder Formats finally stuck! I had no idea this itty bitty thingy on the bottom right corner of the lister prevented any of my changes to stick. Now, each drive finally has its own tab color! Whew.. what a relief. Thank you!