These docs are for an old release.
Info on upgrading to v6
eventBackgroundColor
Sets the background color for all events on the calendar.
String
You can use any of the CSS color formats such #f00, #ff0000, rgb(255,0,0), or red.
This option can be overridden on a per-source basis with the backgroundColor Event Source Object option or on a per-event basis with the backgroundColor Event Object option.