Office 2016 users can change the theme using options available as part of General or Account Settings. In the earlier version, Office comes with the option to change background of Office application but this is not available in Office 2016.
Step 1: Launch any of the office applications such as Microsoft Word. Then click file menu, select options from the list.
Step 2: Navigate to “Personalize your copy of Microsoft Office” section. Then pick your desired option for Office Theme.
Step 1: Click file menu, select Account from the list
Step 2: from the Office Theme drop down, select appropriate from the list. The list of available options are Colourful. Dark Gray and White.