It would please you to know that the "whitish" corolla tube does find a mention in the description of B. prattensis
in the "Revision of the Genus Barleria (Acanthaceae) in India
" by Shankar M. Shendage and S. R. Yadav, published in 2010. I've attached the relevant excerpts of the descriptions of B. prattensis
and B. montana
from this paper.
I am well acquainted with Santapau's work. These are his precise words regarding B. montana: "The flowers are said to be bright blue". Obviously, he was not writing from first-hand experience on this occasion.
All the authors (past and present) agree that the seeds are the key distinguishing factor between these two species.
On the distribution of B. montana, Santapau wrote that "this plant does not occur in Bombay State, or at least I have failed to find a single authentic specimen". According to the paper on Barleria cited above, it does occur in Maharashtra but to a far lesser extent than B. prattensis.
On close observation of the first two images by Alka ji, the corolla tube is indeed whitish. In fact, the white corolla tube is clearly visible in the side view of the topmost flower in the photograph labelled "Barleria_Kothaligad3.JPEG". If we are to rely on this character in the absence of seeds, it would be fair to consider this plant as B. prattensis.
Best wishes, Viplav