Bug?: Internet calendar with (red!) default tag. Not possible to change tag color?

Hello

I’ve subscribed to the internet calendars below. Unfortunately, they all have a red tag by default. I didn’t manage to change that. Is this a bug? Please let me know how to change this annoying red tag to another colour.

https://fcal.ch/privat/fcal_school.ics.php?hl=de&geo=1638
https://fcal.ch/privat/fcal_holidays.ics.php?hl=de&klasse=3&geo=1638

Looking forward to reading from you - thank you.

Kind regards,

Reto