Events that appear as background highlights can be achieved by setting an Event Object's rendering property to "background". Background events that are timed will only be rendered on the time slots in agenda view. Background events that are all-day will only be rendered in month view or the all-day slots of agenda view. The color of background events can be manipulated by targeting the fc-bgevent className, one of your own custom classNames provided by the Event Object's className property, or by explicitly specifying a color with each Event Object's or Event Source's color or backgroundColor properties.

You can change the color of all events on the calendar using the eventColor option. The eventBackgroundColor, eventBorderColor, and eventTextColor options can be used for more granularity. If you want to change the color for events in a specific Event Source, please look at the Event Source options documentation. If you want to change the color for individual events, please look at the Event Object color options.