You're right Early morning light in this room is none too good -- at least, that's my excuse -- but it is much clearer now. I still doubt that they are the stone colours, though, as they look too dark to me, even allowing for the large amount of white in the photo.
Is this the photo on p.168? It's very difficult to tell, isn't it? The exposure of that plate is so skilfully crafted to bring out the detail in a very wide range of light levels. The columns could be lightish, but compare their tone with that of the adjacent goods wagons and they could equally well be quite dark in colour