Is it obligatory to perform ghusl upon seeing clear discharge as a sign of purity, and then seeing yellow discharge afterwards, knowing that she has not performed ghusl after seeing the yellow discharge?

My dear sister, you must perform ghusl upon seeing one of the two signs of purity: the white discharge (al-Qassah al-Bayda'), or complete dryness (al-Jufuf al-Tamm). Yellowish discharge after the cessation of blood, and before the completion of the customary days, is considered menstruation.