Using FullCalendar, is there any way I can programmatically colorize specific days differently than the rest of the days? For example, in the "month" or "week" views, I'd like to colorize days with no events on them "red", and days with some events (but not yet a full schedule) "yellow". Days with a full schedule would be colorized normally (white background). Are there any callbacks or CSS tags I can take advantage of to add this behavior? Thank you.