Never set a custom widget theme.
It is recommended to use the global color theme.
If your application focuses on visual content, e.g. creating or working with images or videos, you might switch the app to a dark color theme corresponding to the global color theme. e.g. switch from Breeze to Breeze Dark, but don’t switch from “Oxygen” to “Breeze Dark”
Provide the option for the user to disable switching to the app specific color theme and use the global color theme instead. You can offer an option for the user to switch to any of the other installed color themes.
Place the option to switch theme in Settings > Designs.