Q.G.,
My first impression the moment I saw that image was that of a distorted true colour picture.
If you select a colour you think could be a remnant of a true colour in a supposed colour original, and see where else it appears in the image, it's hard to keep believing it could have been a colour original.
Why, it's extremely hard even to find a colour (besides that reddish tint) that could come close to what perhaps could have been a true colour in an original colour photograph.
So what i did was sample colours in many places that would have a distinctive colour in an original colour photo, and see where else it appears. For instance, if we assume that the trees are green and look were else that same colour appears, the dirt road, the brick house, the wings of the mill, the faces of the kids, and many other places too are green. Same with other sampled points in the photo.
You can also do a general test, and boost any one of the three colour channels in the digital representation. You'll find then that the effect is not local, not particular to parts in the image (that is not to say that every spot is affected equally; there are colour and tone differences) in a way that even remotely could suggest a colour photo origin.
Mind you, that is still not hard evidence. It could still be an original colour photo in which all traces of having been that has disappeared.
It however is (let's say: ) 'in contrast' to what PE claims, being that there are bits of original colour to be found in the picture.
There are indications (not proof!), apart from the picture itself, about what it could be. Circumstantial evidence. At that time, colour photography, photography itself even, was not a widespread activity. On the contrary.
There are a few known photographers who have travelled and documented the region at around that time. They all worked in B&W. No colour.
And that is something the image collections i mentioned could help with: if from the work of any of these photographers, they may know the image, the man who produced it, and what he used to produce images.