What is the ruling on a woman's fasting if she experiences light-colored spotting while taking menstruation-delaying pills during Ramadan?

The blood discharged by a woman after using birth control pills is considered menses if it appears after her period of purity (the minimum duration of which is 15 days), whether it is flowing or in drops, as long as it descends daily without complete interruption. If it descends one day and stops the next, she is considered menstruating on the day it descends and pure on the day it stops, until she reaches the maximum duration of menses (15 days), after which she is considered to be experiencing irregular bleeding (istihada).