The color that is chosen is dictated by river conditions. For normal winter water conditions where there's six to eight feet of visibility, a dark or medium pattern will work well. The important thing is not to scare the fish. The fly needs to look as natural as possible. When the water is stained or off-color with limited visibility, the brighter fly is mandatory.
Winter steelhead inhabit several areas of a river.
They take the path of least resistance and are often found resting in three feet of water. There are many Western Washington rivers that are better suited to fly angling than others. The ones that immediately come to mind is the Skagit River near Rockport, the Skykomish adjacent to Monroe, and the Kalama near Vancouver, Washington. Also, try the various coastal rivers near Forks. There are several tricks to being successful at winter steelhead fishing with a fly.