Created attachment 120279 [details]
Demonstration 1

SUMMARY
When you select any item inside a folder view and drag-and-drop it somewhere, it will remain with a different "stronger" highlight color unless you successfully move it to somewhere else. 

STEPS TO REPRODUCE
1. Add a Folder View widget pointing to any directory with some files.
2. Drag-and-drop any item to wherever you want, but don't move it (copying or simply canceling it works).

OBSERVED RESULT
The item returns to the folder view with a different, stronger highlight color when selected again.

EXPECTED RESULT
The item returns to the folder view with a regular highlight color when selected again.

SOFTWARE/OS VERSIONS
KDE Neon Testing
KDE Plasma Version: 5.15.90
KDE Frameworks Version: 5.59.0
Qt Version: 5.12.0

ADDITIONAL INFORMATION
See attachment, it's very easy to see the difference in list view mode.