The new feature is available to both Office 365 subscribers and to users who purchased If so, based on my researching and tests, I find that the apps of Office for Mac starting with version 16.20 (Build 18120801) have gotten support for macOS Mojave’s Dark Mode.
For the new Ribbon Refresh, what is it? Please confirm if it is the new feature update “Go Easy on Your Eyes with Dark Mode” mentioned in