Dear Mrs. Mala,
There should not be black thread in the koorai pudavai. Many sarees in green, blue, red etc will have horizontal threads as black.
So, actually it is enough if you check the horizontal threads at the end of the saree.
There IS a method of wearing a madisar with 6.4 mts saree (ie) the saree with a blouse of the same color.
But how can I teach you? Do you live in Chennai?