90 percent of any kind of fishing is putting a fly/lure/bait whatever the kind to a fish,ie location ,location location.Unlike trout I don't believe bass particularly stream bass with the harder conditions they face can afford to be selective as to type/color as long as it looks like something to eat & enters his "strike zone" except in very specific circumstances such as when K3 bass are on the white fly hatch for example.I think this is especially true in murky water,Fox/Rock etal. Years ago there was a similar discussion on our site wherein some anglers argued that big lures were needed to consistently catch big bass.While it's likely that a big bass would prefer a big meal it's also highly unlikely that he'd pass up a smaller one hoping for a bigger one to come along."A bird in hand....".As more ffers came into the club with their reports of big bass caught on flies smaller, often much smaller, than their spin/baitcasting counterparts I think that argument was put to rest. I do agree that after a fish or 2 are caught in a spot the other fish if any in that spot might become reluctant towards that fly.Changing might overcome their reluctance. I primarily change flies to achieve the strike zone bass are in ie switching to a subsurface fly if it seems bass aren't topwater interested, switching from a mid depth fly like a streamer to a deeper pattern like a crawfish if the fish are bottom oriented (& vice versa) and than switching those flies to stay near bottom in different depths/current speeds.