Was it possible for these two weapons systems to be at the same place defending a bridge? Maybe. What you'd want to do is reseach each item, when it went into service and when it went out of service. If there's an overlay of time, the possibility might exist. Then you'd want to research which units used them and where. Further, you'd want to consider risking assets to defend a bridge versus just blowing it and slowing the enemy down with minimal risk to personels and materiel.
Now, as to painting, before March 1943, virtually all German equipment was dark gray. At that point, the high command ordered all eqipment be delivered in dark yellow and crews be equipped with tins of dark green and red brown. Generally, there was no standardized pattern ordered, crews painted as the tank commander or whoever was in charge suggested. There was also no directive regarding the level of thinning or the method of application. Therefore some items had soft edges, sone hard edges; some had very thinned, almost translucent paint and some very dark paints. Some items were left all dark yellow, some were yellow and green, some brown and yellow and some had all three colors is an amazing variety of patterns.
I suspect the 37mm would have gone out of service pretty quickly as armor became impervious to its small shell. Look at the Stuart and Grant/Lee tanks. The Stuart saw some action in Europe as a recon tank only.
This probably only adds to your confusion, but consider this an adventure in learning. There are dozens of books on paint schemes from Ssquadron, Osprey and a host of other.