You can compare file versions of version-controlled files in the Revision Explorer, a two-pane window that displays the version numbers in a tree and gives status details for the selected version number.

Open the Revision Explorer by right-clicking a version-controlled file's node in the Explorer and choosing Revision Explorer (this command may appear directly on the contextual menu or on the submenu of the version control system). In the Revision Explorer, hold down the Control key, select two versions of the file, right-click one of the selected nodes, and choose Diff from the contextual menu.