Ah, Autochromes.
I've always loved the color of this process, and it's hard to duplicate today. I believe the primary "ingrediant", so to speak, was dyed potato starch which made for some interesting grain patterns.
Makes me curious, though. Since Autochrome was a European product that DID find some market in the U.S.A., does anyone know of any pre-1935 color shots of any of the narrow gauge railroads around the country??