I can only speak from fish-keeping experience but here it goes. The brown tint you speak of is the tannins in the wood. Typically in aquariums placing drift wood in the tank is beneficial to the fish because the tannins that leech in to the water actually lower the ph causing the water to be more basic. Just like some people add a small pinch of salt to their aquariums- the lower ph is good for a fishes coat. How this explanation relates to bass fishing though, I have no idea I guess a healthier-coated fish is a happier bigger fish hopefully!
