Here the following logic applies:
All settings apply to the next element, which is inserted! Thus not "retroactively". If you insert e.g. a text, the default color given in the menu default settings is used. If you change then the color in the menu default settings, nothing will be changed at the already existing text. But the next text which is inserted, gets the "new" color. An exception of this rule concerns the 'Default HighLight/Activated properties': These settings are applied to the main menu as long as nothing(!) has been added to the project. If you add a text, film, picture..., any changes in the menu default settings apply only to the next inserted menu (Titlesetmenu or submenu). To change these settings for the main menu (or also every other menu) after an element is inserted: Right-click on the menu background and choose 'Menu properties' or select 'Format' - 'Menu (Actual)' from the menu bar.
You may change all default settings anytime, except the authoring engine and the 'General Settings' shown below:
If you click on OK within the default settings dialog, the settings are used for the current project only (or until you close GFD respectively). Only if Save is clicked, all default settings are saved permanently in the registry.
Some settings may also be saved as 'presets'. This enables you to change default settings for different kinds of menus (main/chapter) quite fast. Only 'reasonable' settings are saved/loaded as Presets (no permanent nor the shown general project settings)
As there are more than 100(!) topics in the default settings, these are spread over several tabs: