https://thenextweb.com/apps/2020/07/06/google-finally-rolls-out-dark-mode-for-docs-sheets-and-slides-on-android/

It’s been a long time coming but today Google finally brought dark mode support to its most popular office software on Android, namely Docs, Sheets, and Slides.

If you have an Andriod 10 device or later, the theme should automatically activate if you’ve enabled your phone’s Dark theme, which you can do by going to your device’s ‘Settings,’ tapping on ‘Display,’ and then ‘Theme.’