calendar-mark-days-named

calendar-mark-days-named is a compiled Lisp function in `diary-lib.el'.

(calendar-mark-days-named DAYNAME &optional COLOR)

Mark all dates in the calendar window that are day DAYNAME of the week.
0 means all Sundays, 1 means all Mondays, and so on.
Optional argument COLOR is passed to `calendar-mark-visible-date' as MARK.