Devir Kahan offers some tips on consolidating your calendars.
I switched from Google Calendar to iCloud recently, and I’d been meaning to switch to one calendar for all events. While having a different colored calendar for Fun Events, Family Events, School Events, Due Dates, Appointments, etc. is nice to look at, it just adds an extra step to event creation. For me, it also undermined the efficiency of apps like Calvetica and Agenda, which are designed to create events with as few taps as possible.
Devir’s method works flawlessly, only takes a minute, and removes considerable friction in any calendar app.