To change the colours of your external phone calendars and friends' calendars in Howbout:

1. Head to the Calendar (🗓️) tab
2. Tap the ‘You’ button in the top left corner of the screen
3. Toggle on the calendars you want to see on your Howbout calendar
4. Tap the colour droplet next to your and your friends' calendars to change the colour 

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