Why are items in a Calendar view different colors for different users?

Our team uses a calendar connected to about a dozen boards to get an overview of the month’s work. Items from each board are all the same color and each board is its own unique color. However, the colors differ from user to user. What may be green for me is blue to someone else.

I have tried to see if this is because of our theme settings, but that does not change anything.

Is there a way to set the colors so that they are the same for everyone?

I was not actually aware that this is how the calendar functions! Perhaps it has to do with the permission settings that each of the members have for the connected boards?

Happy to hear more !