Should i leave them be until totally brown?
Allamanda Seed Pods That Are Brownish Green
Certified GKH Gardening Expert
Yes, the longer you leave them, the better the chance that they have to be able to germinate. Take them right before they fall out if possible.
Here is an article to refresh you on their care: https://www.gardeningknowhow.com/houseplants/golden-trumpet/allamanda-indoors.htm