This version of the Royal Wulff uses a green body.
In 1985 I was experimenting with using the green colour instead of the red and would buy the Royal Wulff and over wrap the red with a bright green thread. It worked so much so that in the Video "wilderness flyfishing" (1987) John Goddard is seen to say " I caught it on that bloody Green Wulff of yours". After that we sold it for many years in the old Alan's flyshack and it seems to have become a pretty much accepted variant of the Royal Wulff. I think in the New Zealand summer it works better as green terrestrials are a feature of the summer insect life.