Google Inc. recently launched its newest mobile operating system, Android Oreo. Previously the company had said that it might introduce support for themes in Android Oreo operating system, and thanks to xda-developers we now know that the new operating system supports Overlay Manager Service (OMS) and Runtime Resource Overlay (RRO), it also comes with an interface for enabling and disabling themes. However, the feature is not yet available to the public and you will need to use a command line to enable it.
Google now seems to be wanting to introduce a full theme manager into the operating system. xda-developers also said that the company has made many changes in the Android Oreo operating system since the developer’s preview, which suggest that the company in a few more updates will introduce a full system theming engine built in the operating system.
The permissions required to run the command lines are currently only held by system apps and apps with root access. It will make it much easier for OEMs who like to put a custom skin over the operating system, as this would allow them to only put a theme instead of developing a whole custom ROM. It will also benefit the users as if the OEMs only put a theme over the operating system the base will stay as stock Android which would help in pushing out updates faster.
Currently, this feature is of no use as for now you can only manage previously installed themes and cannot install new themes. Installing a new theme requires access to a directory which is restricted from user space. The company has not provided an app to theme the device yet, and until that is done these new code lines are you no use.