How to change icon?

In the nextcloud-client application there is the light gray circular icon with a white check mark inside.
This icon is barely visible with my computer theme in the notification area.
How can I change it? I have not found where it is stored. (Ubuntu linux based system)
Thank you


You can make the icons monochrome via settings at least. Probably that makes it better readable in your case.

But no idea how to change it manually, or if even possible without compiling it from source.

Apropos source, there you find the icon set:

Thanks a lot.