When Altium designer is connected to the SVN repo, it shows the status of each file under version control (Green = OK, Red = different from the one in the repository).
To connect to a remote SVN server, you need to input the server's URL and connection method (HTTP, HTTPS, SVN, file or FTP). Altium's client is old and is not supported in the current version of the SVN server, so you need to use a newer client, ToroiseSVN is an excellent choice and can be specified in the Data management/Version control option tab in Altium designer's preferences.