ANSWER:

If a whole day passes and she is totally dry, she must take ghusul and start to pray. The colored discharges after her purity are not considered from her menses. She should not stop praying until she sees the flow of the blood again.  

What are minimum number of days of a menstrual cycle? If a woman gets regular periods for two days only and gets dry for next 1 to 2 days followed by slow discharge (sometimes red and sometimes Brown) for next 2 or 3 days, can she say prayers in those 2 dry days and also in next days in which she gets slow discharge?