Steps to replicate the issue (include links if applicable):

Open the Wikipedia Android app (F-Droid version 2.7.50549-r-2025-09-17)
Switch to Black theme
Open any image in the image viewer
Highlight text (e.g., image caption text)

What happens?

The text highlight color is now a transparent purple, which blends into the background and is difficult to see.

This creates accessibility concerns, especially for users with poor eyesight or for those frequently working with image captions.

What should have happened instead?
Highlighted text should be easy to see in Black theme.

Software version:
Wikipedia Android app, F-Droid version 2.7.50549-r-2025-09-17
Device: Samsung SM-A035M (SDK: 33)