On the Repository tree view, the red lock appended to the repository item shows that the item is already edited by another user.
But you can still open and view the locked item in the design workspace in a read-only mode. Right-click the item in the Repository tree view, and then click Open to view the item content.
Alternatively, you can get read-write access to locked items by opening the project in offline mode. For more information, see Accessing items of a remote project in offline mode.