1. (In English, but worthwhile)  O'Brien
"Some Principles of 18th Century Harpsichord Stringing and Their
Applications"

compares gauges/tensions of several schools. On the 1774 Ruckers/Taskin
the wrestplank is stamped with Gauges and "blanc" for iron; "jeaun"
 (sic) for y/b and "rouge" for r/b.

This article was sent to me and I do not know it's source. Someone out
there will.

2. In French:
Michel Corrette  "Le Maître de Clavecin pour l'Accompagnement, Méthode
Théorique et Pratique." (1753)

See Chapitre XXI. "Les numero des cordes dont il faut se servir pour les
clavecins et les epinettes."

  (likewise, Corrette uses rouge, jaunes, blanches)


If you would like these and cannot find,  I will be happy to copy and
mail. Contact off-list.

Ran