Windows 10 has a dark theme, macOS has a dark theme, and Microsoft's Office also has a dark theme to accommodate these. The point is that at least in the case of Word, no dark theme or variation so far, has been truly dark.
Document pages still have white background although the rest of the interface of the popular text editor is black and dark gray. That is finally about to change.
New dark mode for Word
Microsoft recently announced that the Word accessibility team is working on a more extensive dark mode, one that finally has a white canvas. It's a feature that users have been asking for for years, and it's beyond puzzling that it took so many years to implement.
The new dark mode can now be tested by members of the Office Insider Program. It is worth noting that the new dark mode does not replace the previous one, it is simply one more option.
You can switch between light mode, dark mode with white pages, or dark mode with black pages. The option appears in the ribbon menu in the print mode page options, as long as you have dark mode active.
Dark mode is activated by clicking File> Account> Office Theme> Black. The new option is now available in the beta channel for users using version 2012 (Build 13518.10000).