A great dragon fly nymph imitation.
Dragonfly nymphs will adapt to the colour of their surroundings.
This is another overlooked fly. There are half a dozen different types of dragon fly nymphs, but most people insist on fishing flies such as a Papa Roach, often overlooking the other types such as the Lake Dragon. I'd diversify a little and give this bad boy a try.
Fish it slow near weed beds on a floating line.