A friend of mine posted this on another list. I'm copying it here, but including as many original references as I can...
Mike.Color Photos From the World War I Era
Written by Alan Bellows
on July 29th, 2006 at 9:06 pm
This is a classic Damn Interesting article which was originally published on 04 December 2005.
Nilova Monastery: Color film was non-existent in 1909 Russia, yet in that year a photographer named Sergei Mikhailovich Prokudin-Gorskii embarked on a photographic survey of his homeland and captured hundreds of photos in full, vivid color. His photographic plates were black and white, but he had developed an ingenious photographic technique which allowed him to use them to produce accurate color images.
He accomplished this with a clever camera of his own design, which took three black and white photos of a scene in rapid sequence, each though a differently colored filter. His photographic plates were long and slender, capturing all three images onto the same plate, resulting in three monochrome images which each had certain color information filtered out.
Sergei was then able to use a special image projector to project the three images onto a screen, each directly overlapping the others, and each through the appropriately colored filter. The recombined projection was a full-color representation of the original scene. Emir of BukharaEach three-image series captured by the camera stored all of the color information onto the black and white plates; all they lacked was actual tint, which the color filters on the projector restored.
Tsar Nicholas II fully supported Sergei's ambitious plan to document the Russian Empire, and provided a specially equipped railroad car which enclosed a darkroom for Sergei to develop his glass plates. He took hundreds of these color photos all over Russia from 1909 through 1915.
There was no means to develop color prints at that time, but modern technology has allowed these images to be recombined in their full original colors. The U.S. Library of Congress purchased all of Sergei's original glass negatives from his heirs in 1948, and in 2001 a beautiful exhibition was produced to showcase Sergei's photos, called The Empire that was Russia.
Color Photo from World War I FranceAround that same time, in 1907, the first practical color photographic plates were introduced to the world by the Lumière brothers in France. The plates were called "Autochrome Lumière," and they were made up of microscopic potato starch grains which were dyed orange, green, and blue; sandwiched between black-and-white film and a piece of glass; then coated in shellac. The tiny starch grains acted as color filters, making the film essentially a mosaic made up of many tiny pieces.
Once the black-and-white film base was developed, the dyed starch layer which had acted as many tiny color filters when the photo was taken now did the same task in reverse, giving the color back to the underlying image. The technology was a bit crude and grainy, but it was able to capture full color images which turned out looking rather impressionistic.
Marine RiflemenAutochrome film was expensive, slow and rare, so it didn't see a lot of use by the general public. But when World War One broke out in 1914, the French army began photographing soldiers and scenery, and some of their photos were taken with this new color film. As a result, a large proportion of color photos from that time are images of French soldiers in the field.
Because of the efforts of the French army photographers, there are beautiful color images of soldiers in the trenches, military equipment, ruined buildings, and villages, among other things. Autochrome plates age remarkably well due to their construction, so many of the originals are still in pristine condition today.
Autochrome remained as the primary color photograph medium until Kodachrome was introduced in 1935, and Agfacolor in the following year. Aside from Kodachrome, most modern color films are still based on the Agfacolor technology.
Further reading:Library of Congress site on Prokudin-Gorskii's photos of RussiaLarge gallery of French WWI photographsDetailed information about Autochrome film