Default event color

How do you change the default color for calendar events under an exchange account?
All the events by default are purple and I want them to be orange. Can I change all the events all at once vs one by one?

Right-click on the calendar folder and choose Calendar Color.

By default, events will use the tag color if they have one over the calendar color, but you can change that setting in Menu > Settings > Calendar > Source of events color if you use tags.