In a first experiment, http://chromebrown.blogspot.com/
it was demonstrated that Green Chromium Oxide may produce browns :
Here we have a compromise between Brown and Green
About the Author: Edouard Bastarache lives in Québec, Canada, and has a colorful history. He studied surgery, internal medicine and neuroendecrine physiology and was a medical researcher and consultant in Occupational & Environmental Medicine between 1971 and 1983. Since 1983 he has been a full-time consultant in occupational and environmental medicine. At the same time as his medical studies, he studied ceramics under Julien Cloutier at La Boutique d'Argile (The Clay Shop) and later also taught at the same school. Bastarache now lives in the Sorel-Tracy region of Québec, near the St. Lawrence river. He uses waste materials from steel plants located in the area to color many of his glazes and clays. He fires most of his work to cone 9 1/2 in reduction in a 60 cubic foot downdraft gas kiln.
His first book, "Substitutions for Raw Ceramic Materials" is available in 8 languages: French, English, German, Italian, Spanish, Portuguese (Portugal & Brazil), and Esperanto.
He also recently published Toxicology Ceramics Glass and Metallurgy, in English and French