What is the ruling on yellowish or brownish discharge if menstruation is irregular, accompanied by some spots of blood, which then stop?

There is a difference of opinion among scholars regarding yellowish and brownish discharges (ṣufrah and kudrah): Some consider them menstruation absolutely, during the time when menstruation is possible (the view of the majority). Others do not consider them menstruation absolutely (Ibn Hazm and Ibn Taymiyyah). And some differentiate. You may follow whichever scholar you wish. If you act upon the opinion of those who do not consider them menstruation unless preceded by blood, then yellowish and brownish discharges are not menstruation. As for a small amount of blood, it is considered menstruation by the Malikis and Ibn Taymiyyah, while the majority holds that the minimum duration of menstruation is one day and one night. According to the view of the majority, who consider yellowish and brownish discharges to be menstruation, as soon as you see them, you are in a state of menstruation.