How to Apply a Theme to a Document in Word 2016
You choose a theme in Word 2016 by using the Themes button found on the Design tab. Built-in themes are listed along with any custom themes you’ve created.
Each built-in theme controls all three major theme elements (colors, fonts, graphical effects), changing your document’s contents accordingly. Hovering the mouse pointer over a theme changes your document visually, which is a way to preview the themes. Click a theme to choose it.
Because a document can use only one theme at a time, choosing a new theme replaces the current theme.
To unapply a theme from your document, choose the Office theme or the menu command Reset to Theme from Template.
If you would rather change only one part of a theme, such as a document’s fonts, use the Colors, Fonts, or Effects command button on the Design tab.