To change the colour of your group and its events:

1. Head to the People page by tapping the people icon at the bottom of the screen
2. Select the group you want to change the colour of 
3. Tap the colour wheel in the top right corner
4. Select the colour you want to change the group to
5. The group and all of the group's events will now be set to your new colour. Any specific group events that you've already set an event colour for won't be affected

Please note that while viewing a friend's calendar, all of your own calendars and events will temporarily become one colour to avoid you getting mixed up 😌