At least currently, the \\server level (but not anything below it) is delegated to the Windows shell. (Since you can't do much in that folder except double-click something to navigate into it, so we can't add much value by handling it natively, at least in terms of functionality. We might handle it natively in the future just to help with aesthetics for people using dark themes.)
The Windows shell doesn't support color customization.
Although you can turn on Preferences / Display / Options / Enable background images in virtual folders to apply the background color to that folder, it won't work well with dark themes because the text color will still be black, and you'll end up with black on black.
(Same with Recycle Bin.)