Slot the 3.8mm tungsten onto the J100 and start black Sumo thread. Black keeps the body dark without going fully black, which is the tone Vasies wants for deep pools and murky water.
Tie in grey partridge barbs as a tail and the green UV Hot Spot Thread as the rib at the bend.
Dub a body of salt and pepper squirrel forward to the 65% mark, building it deliberately conical. Thin at the tail, noticeably fatter at the front. That taper is what lets the partridge hackle stand open later instead of folding flat.
Rib forward with the green Hot Spot Thread in open turns and tie off. Vasies fished identical flies ribbed green and orange in the same pool and the green was clearly more productive, his theory being that fish have simply seen too much orange and red.
Dub a small A9 Atomic UV thorax behind the bead, then take one or two turns of grey partridge neck hackle and sweep the barbs back.
Whip finish behind the bead. Fish it in fast currents and behind rocks and structure, where the contrast shows up in broken or coloured water.