These docs are for an old release.
Info on upgrading to v6
eventBorderColor
Sets the border 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 borderColor Event Source Object option or on a per-event basis with the borderColor Event Object option.