When must a woman perform ghusl if intermittent menstrual bleeding—in the form of brown or light-colored discharge—continues after the original bleeding has stopped for several days?

If a woman sees one of the two signs of purity (dryness or the white discharge), she must perform ghusl (definition) (ritual bath). If bleeding resumes after that, within a time frame where it could be menstruation, she is considered to be menstruating again. However, yellowness or brownish discharge after seeing the sign of purity is not considered menstruation, unless it occurs during her usual period.