If you download and enlarge this image , you could see the starch grains.
A lots of people uses gaussian noise of the photoshop for to create a look like grainy autochrome but I think true color noise can be adapted by Perlin Noise.
Perlin Noise is what you see at shoot kill multi player games walls , ground everywhere. Realistic noise
It is used for all games and renderings and Perlin got academy award.
I dont know how you will use this information but it is very very important.
May be ALT printers will prepare their negatives by this way.
Or you can write a plug in to mimic the look of autochrome.
ALT people will enjoy and the digital ALT inkjet people also
Mustafa Umut Sarac