Is the white discharge that appears after blood, kudrah, and sufrah considered the end of menstruation and necessitates ghusl, or is it obligatory to wait for the complete cessation of the sufrah?

There is no significance to seeing yellowish discharge after seeing the white discharge, and that is not considered menstruation. This is because yellowish or brownish discharge after purification does not have the ruling of menstruation. Also, due to the saying of Umm Atiyyah: "We did not consider the brownish and yellowish discharge after purification as anything." And the white discharge is the clearest sign of purification.