I believe I found out why he looked so dark. My large BN pleco usually stays on the right side of the tank in or under the cave or under the driftwood. When he's hungry though, he ventures over to the other side of the tank and the bolivian ram has to move somewhere away from his usually hangout. I think his turning dark colored is due to stress of the pleco nearby.
When the pleco is not in his territory, his color is more like his color in my sig.