Whether the user uses Dark theme or a Light Theme:
There are many methods to apply awareness in themes.Since most of them are XAML-based,i'll give you an alternative way.
You can also apply image based awareness in themes if its light or dark,doesnt matter.
The cheat is you need to have a Transparent Background with White colored image inside.
You're unable to view it but it works on your apps:
Look at the example below:
Sample Home and Question images here:
Light Theme:
Dark Theme:
Hope its useful!