A while back, I heard that there existed a few colour photos, taken during World War I. So far, I failed to find out more, but today, I came across a few samples.
I know nothing about the actual photographic process etc. To navigate click on the numbers (or use “vor” for “next” and “zurück” for “previous”).
Update: I wasn’t too satisfied with the state of this post so I did some research. I came across this site that contains explanations and many photos/samples. The actual colour photos - there are many colourized b/w ones - were done using Auguste and Louis Lumié‘½e’s autochrome process. There are some more samples on this site. And if you really want to get some of those photos - plus the actual history of World War I - check out this book.
And Simon Smith just sent me the link to the French archives that contain the photos (thanks!). If you don’t speak French: you access the photos at the top right-hand side. The photos are sorted by location. For each location, there is a list of the photos; on those pages without thumbnails you view the photos by clicking on the icon that looks like an eye.