The Inspector view shows all of the metadata for the currently selected item in the Sidebar. To show the Inspector, use the View menu or press the Inspector button in the toolbar. You can use click on the tabs at the top of the Inspector to view the metadata for the selected entry's containing journal, and the default settings for all entries and journal in the Document section.
Certain kinds of metadata can be inherited from whatever contains the entry or journal. For example, the background color of an entry can be inherited from the journal that it is in. If that journal does not have a specified background color, MacJournal uses the default setting in the Document tab. In the Entry tab, you can change the background color to something that is custom, you can set it to None (in which case white will be used), or you can set it to Inherit the color of its journal (which is the default). If you want to change a setting like the background color for all entries in a certain journal, use the Journal tab to change it. If you want to change the setting for all journals and entries in that document that don't have a custom setting, use the Document tab.
If you want to change metadata for more than one item at a time, select all the entries you want to change and use the "Batch Change" menu item.