Selecting a Theme will set colors and fonts for internal elements such as smart art and items found in Quick Parts. For example, the default text box picks up fill color and font specs from the Theme.
We cannot directly edit a Theme. We can modify the colors and fonts in a Word document and then save out a New Theme. So, the procedure to create a variation we must alter the Theme of the current document and, after we have made the desired changes, select "Create New Theme." After giving the new Theme a name we may choose to delete the old Theme.
The graphic below shows the relationship between the Themes color settings and where they appear in the document color settings panel.