Well, how is this for inconclusive.....My August 2013 photos do not show yellow, but the end section of the bridge I think you photographed is behind dense foliage. You can imagine how that brush that is bare in your photo would look in August.....completely leafed out. So if there was yellow paint I wound not have seen it.
Furthermore, the yellow paint was probably applied before that bush grew there. In my photos of the bridge, there are exposed bridge ends that would be a whole lot easier to paint than behind the bush. And obviously who would paint behind a bush anyway? So one could reasonably assert that the paint proceeded the bush.....but who knows by how much?
And to extend my "logic" a few steps more, why paint just one end yellow for safety? I have displayed my random shots below.
If you drove on to cross the Snake at Central Ferry bridge, you saw the old bridge at 46.524160, -117.783569 which I suspect either of us would identify as a typical early last century design. Young folks like you and your wife probably jogged down to take a look. I did my looks by telephoto lens!