This issue is being tracked already:
Issue 2080 – More contrasting or configurable file panel selection color (particularly for the dark mode)
You can vote for it there.

The dark mode of the file panel is rendered by Windows. It's not controlled by WinSCP at all. As the dark mode support in Windows is new, this might get improved eventually by some Windows update.

You can change between light and dark mode as you like in Preferences:
https://winscp.net/eng/docs/ui_pref_interface

Hi

First dark mode is great and really needed. But unfortunately I have issues as I can not see which files are selected and which not.

Can you give us an option to change the selected file color?
Or at least to switch from light to dark mode at will.

For example in the attached image the Imagegroup.php file is selected but this is not visible at all.

Best regards
Waldemar