What is the ruling on prayer during the first days when a red spot of blood appears and disappears before the onset of the regular menstrual period?

The spots a woman notices during a three-day period, if they do not last for a full day and night, are not considered menstruation according to the majority of scholars. This is because the minimum duration for menstruation, in their view, is a day and a night. Therefore, it is obligatory to perform istinja (definition)' (washing the private parts) from these spots when intending to perform wudu' for prayer.