I've been treated several times over the past 6 months for green vaginal discharge. why does it continue? what is the cause of it?

Menopause changes: Sometimes when a vaginal discharge persists, it could be that the vaginal tissue is going through a process called atrophy which means that it is no longer as nourished as it once was with estrogen. It is a hormonal change. Just be sure that you have had a culture and vaginal exam to ensure that there are no other causes. 42 is a little young to have the hormonal issue, but it can happen.