Information on 18th-c. dyeing in India has largely on based on a few sources, especially the Beaulieu manuscript (1734), the letters by father Coeurdoux (as published in the influential Lettres edifiantes series, 1743) and the earlier Roques manuscript (c. 1679).
Other sources largely relied on earlier sources, or supplied variations on the recipes, combining years of experience in European counterfeit imitation of Indian fabrics and actual Indian practice (read: Indian practice as described by travelling sources).
I found information in Buchoz' Les secrets de la nature et de l'art that seems to have been neglected by scholarship. In the 4th part (p. 165), on textile dyeing, Buchoz states: 'M. Guillard, Chef du Comptoir de la Compagnie à Aganaou, distant de quarante lieues de Mazulipatan, ou l'on en fait de fort beau, m'a envoyé le détail de cette opération' (of indigo dyeing). He also quotes extensive recipes of green and red, however without mentioning the source, but differences with other descriptions are clear. And not unimportant: all these descriptions are highly detailed.
It is hard to say whether Buchoz' notations are really 'messages from the field'.
He certainly has his reputation against him, as reputed polygraph. Many of his works are more known for the quality of their engravings than for their scientific value.
Besides, in his large and encyclopedious works, accuracy had often been by speedy output and popular trivia.
Maybe this explains why no-one seemingly ever took notice. Not only Indian dyeing, but also Chinese colour-producing is amply discussed in the book. At the moment I am still reading and comparing, I will publish more when conclusions seem to pop up.
.. to be continued..