Menstruation period does not end unless the blood within the period stops completely. This blood may be black, red, greenish, yellow, or even blurred earth colour. The discharge from a woman who has completed her period would be white. Once white discharge is seen, any other opacity after that is not considered as menstruation.
Narrated Um ‘Atiya:
“Umm ‘Atiyah said: ‘We used not to regard yellowish and brownish discharge as anything important.” (Bukhari, Hayd, 26; Abu Dawood, Taharat, 117; Nasai, Hayd, 7)