Basically have a little icon or different shading to show logged in users which of the announcements is public and which one isn't.
From Trello:
Announcement numbers are not relevant to the users, so no need to display them in bold for every announcement. But consider using different colours for public and non-public announcements so they are easier to differentiate in logged-in mode
public announcements should display for logged-in users as well. It would be nice if internal and public announcements would have different colours so they can be easily differentiated.
Basically have a little icon or different shading to show logged in users which of the announcements is public and which one isn't.
From Trello: