One of the less-noticed features of Office is the ability to change its basic design theme. A new group policy option now allows administrators set that theme as a default for all users.
The Office IT Pro blog describes how to add the option, which requires new Office administrative templates and end user client updates.
The setting isn't entirely prescriptive; users still have the option to change from the suggested default theme to another, and any user who has already changed their theme can't be forced back to the recommended corporate default. That said, given that the theme option is confusingly buried under Account options, we're not sure too many people will ever notice it.
Setting the Office Theme using Group Policy [Office IT Pro Blog]