What is the ruling on my ignorance regarding the sign of purity from menstruation, given that I used to perform ghusl upon seeing yellowish or brownish discharges after the cessation of clear blood, with dryness present at times? Was what I did correct?

A woman recognizes purity by one of two signs: dryness or the white discharge (al-Qassah al-Bayda'). Yellowish or brownish discharge connected to blood is considered menstruation. If you performed ghusl (ritual bath) believing that menstruation had ceased, and your prayers after attaining purity were invalid due to lack of purification, then you must make them up according to the majority of scholars. It is more prudent to make them up to avoid scholarly difference. If you are unaware of the number of prayers, then make an effort to determine them and make up what you believe will absolve your responsibility.