https://www.techradar.com/news/ios-13-dark-mode

Ready to tone down your iPhone and iPad brightness with the iOS 13 beta update next week? That's exactly what Dark Mode will do, according to the latest Apple leak.

The first screenshot of iOS 13 Dark Mode has surfaced on 9to5Mac, and it shows a black theme where we once saw an all-white background for the Apple Music UI. The switch to Dark Mode should be as simple as tapping a button in Control Center.