Does the expulsion of a brownish discharge a few minutes before the Maghrib Adhan, at the time of the menstrual period, invalidate the fast and necessitate its making up?

The descent of menstrual blood, even for an instant before sunset, invalidates the fast and necessitates making up for that day, regardless of whether it occurred at the beginning or end of the day. If the yellowish or brownish discharge occurs during the regular time of your menstrual cycle, it is considered menstruation, and you must make up for that day.