SUMMARY
Plasma's calendar widget, when set up with the PIM events plugin and a .ics calendar file selected, changes the folder color on KOrganizer, as well as the color of the events on the widget, assigning a random color based on the interaction with the calendar grid. All of the colors changes by:

- Opening the calendar grid;
- Closing the calendar grid;
- Moving the calendar to the next month or previous month.

STEPS TO REPRODUCE
Note - I have only tried with a .ics calendar file. Your mileage may vary with other calendar files.
1. Have a .ics calendar added on KOrganizer
2. Enable the PIM calendar plugin on the calendar section of the digital watch configuration
3. Select the .ics calendar on the PIM events section of the digital watch configuration
4. Open the calendar grid

OBSERVED RESULT
Each event has a different color other than the one set by the user on KOrganizer. On KOrganizer the calendar folder color changes as well and does so when interacting with the widget in the ways described on the summary. The event colors on the calendar widget change as well. The folder color on the month grid on KOrganizer does not change.

EXPECTED RESULT
The color of the events are the same as the folder color set by the user on KOrganizer.

SOFTWARE/OS VERSIONS
Operating System: Fedora Linux 40
KDE Plasma Version: 6.1.4
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2
Kernel Version: 6.10.6-200.fc40.x86_64 (64-bit)
Graphics Platform: Wayland

ADDITIONAL INFORMATION
I have a video showcasing the bug, but it's too big to attach :(