Visual Indicator on Folder/Project shared outside my company

It'd be very useful to have a visual indicator for which projects/folders are shared externally, outside the user's organization. This would remind all that all project/folder info will be seen outside the company. Without this indicator, it's not clear to casual collaborators that normally open references to company confidential or partner characterization information will be seen by that external partner/collaborator.

I have used collaboration successfully in the past, and prefaced such joint projects as EXTERNAL - which works, and I'll continue using it until a better visual cue is available.