Sculpins (aka "bullheads") are often eaten by large, predatory trout, both in rivers and in lakes. This is one of many sculpin patterns that anglers have devised.
Olive and brown are two other useful colors.
How to Fish
Use a sink-tip or full sinking line and a count-down-and-retrieve or slow retrieve presentation. Sometimes make the fly move with quick darts: give it a short fast strip, then let it sit, then strip again; and so on. The main thing is to be at the right depth (it will vary) and to make the fly move like it is alive.