My take is that the photo shows the bridge is or was painted black. The sun is behind the photographer, and its mid-late afternoon. See the sun on the tank and station, etc. Since this was likely taken in the 1940's it could have been repainted silver later on to match all the others that were silver at the end. The shot also shows the end of the "San Juan" eastbound at the station, so its before 1951. In some recent video released footage Earl commented to me that the bridge at Antonito, and Los Pinots were freshly painted, and perhaps the last time they were painted in the 60's. I have never seen shots of black bridges, but that doesn't mean they don't exist. Most of the photos before 1950 are in black and white therefore its tough to tell colors back then. We have a shot of the bridge in our new Rio Grande Steam Passenger Trains show. He guy rode to Gato, and got off and you see the bridge in the distance, then the Eastbound comes into the station(Bridge in background again). Its a dark sequence and late in the afternoon so the bridge color would not be obvious one way or the other, but the footage is in color. I remember seeing it in 1966 and 1968 but of course then it was silver.
Greg