To change the background color and design of all your Office programs, go to File > Account from any open Office program, and then click the drop down menu next to Office Theme. (Or, go to File > Options > General > Office Theme).
The colorful theme aligns with the visuals of our modern Office apps by bringing their primary accent color to the ribbon.
The colorful theme in Excel 2016:
The colorful theme in PowerPoint 2016:
The colorful theme in Word 2016:
Dark gray theme
The dark gray theme is perfect for those who prefer a softer take on high-contrast visuals. Here's an example of the dark gray theme applied to PowerPoint 2016:
The Black theme provides the highest-contrast visual for your Office theme. Here's an example of the black theme applied to PowerPoint 2016:
The white theme displays the classic look of Office. Here's an example of the White Theme in PowerPoint 2016: