Costumes in the North-East

In North-East India, how easy is it to guess tribal affiliations through costumes?

While driving up the Guwahati-Shillong road, one of the first things that strike you is the toga-like dress women wear while they go about their lives. Vendors seem to prefer a more utilitarian combination of skirt + blouse + toga while the younger ones seem to prefer jeans + t-shirt + toga. 

At first I thought all these ladies were all Khasis. The only other matrilenial community in India, apart from the Nairs in Kerala. However, after a visit to the amazing Don Bosco Museum in Shillong it was quite plain that there could be no simple generalizations. 

Khasis traditionally wear a covering garment across both their shoulders while the the Jaintia women prefer to tie-up on one side. 

Now, some women prefer to have the knot on the left, while others have it on the right. Does it mean anything? I don't know...