The mentions option lets you mention or tag another user in a specific message. This is useful if you want to capture the attention of a specific user.
The mentions for the admins look like this.
It’s in red as it signifies an admin user.
The mentions for the non-admin user look like this.
It’s in green as it signifies non-admin users or regular chatters.
This is how it looks like when you mention someone in the chat.
The username of the one mentioned will appear in blue.
Here’s a video that shows the mentions option in action.