A scope is a track: personal, business, birthdays, or one you add. Events live in events/<scope>/. 
calkit scope list --json
calkit scope add travel --name "Travel" --color "#0f766e" --description "Trips" --json
calkit scope edit travel --name "Travel & lodging" --json
calkit scope rm travel --reassign personal --json
--color is #RRGGBB. You cannot remove a scope that still has events unless you --reassign them. Reminder items can use the same scope ids. Create the scope before assigning reminders to it.