The visual theme change occurs immediately, and assuming you choose Classic you will find the colorful window dressing is stripped and returned to match the grays of whatever the Mac OS theme is set to.

You will get a little notification informing you that changing the Microsoft Office theme will impact all other Microsoft Office apps. Look under the ‘Personalize’ section to find “Office Theme:” and choose “Classic”.Pull down the “Word” menu and choose “Preferences” *.For the walkthrough here we are demonstrating this process in Microsoft Word. In other words, if you change the theme in Microsoft Word, it will impact the theme in Microsoft Excel as well, and vice versa. This change can be invoked from any of the Microsoft Office apps, and the theme change applies to all other Microsoft Office apps too. How to Change Microsoft Office (Word, Excel, Powerpoint) Theme on Mac If you’d like to change the appearance theme of Microsoft Office apps, including Word, Excel, or Powerpoint on the Mac, so that they visually match the light theme or the dark mode theme appearance of Mac OS, you can do so with an adjustment in the Microsoft Office app settings.

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