About ocrhe, this pigment used from the very first ages of humanity,
you can see :

… the web site of Okrha
(association which purpose is to perpetuate ocrhe knowledge and use) :
Okhra

you can also visit another web site, written by a "pays d'Apt" enthusiast !
(french only, sorry) :
what about ocrhe ?
history of ocrhe
producing ocrhe