There's nothing particularly special about the following streamer, except that it's largely white. And it does ride with the hook up, somewhat like a Croppie Jig. And white seems to be what's working now, during late fall on Montana Rivers. I fished sculpins and black leeches for several hours last Friday, on the Missouri, while only catching a few fish--while my buddy knocked'em silly with a white flyrod jig. He gave me one his white jigs and I started to wack'em too. This went on for several hours. There was no mistaking the lack of action on dark streamers, and the lights-out action on light ones.
The reports coming in from the Gallatin and Madison are much the same. I didn't get a Yellowstone report recently. But I doubt it's any different. Forget dark. Go with white or light. But it isn't always like that. Sculpins are an early summer goto way to fish. Why white now?