Grayling are beautiful fish, extending the fly fisher's callender and offering a real challenge too. At times they are willing to let you wade amongst them, snaffling up any fly that happens to pass by. The next day they can be really spooky, tolerating little in the way of disturbance or, indeed, anything that appears to be against the norm. They can mouth and reject a fly in seconds I am certain they take and refuse nymphs and bugs far more readily than we are aware. If they are willing to move to a dry fly, they can ascend and return in split seconds leaving you bewildered that there was even a rise.
Now, return to the nymphs. You'll read lots about grayling coming to heavy bugs, often brightly coloured and fished as a team. True. However, when they are a little more suspicious, it is the thinking angler that will be successful, choosing to adapt their fly choice and aim for something a little more imitattive. The Pheasant Tail nymph takes some beating under these circumstances. But even then, a little colour can help add a little something extra. Here's an example of the PTN tied with a red hotspot - just holographic tinsel tied behind the thorax. Another dimension to the fly box; improved chances of success:
Hook: Partridge BIN #14
Thread: Powersilk, 10/0 olive
Tail & abdomen: PT fibres
Hot-spot: holographic tinsel, red
Wing buds: PT fibres
Legs: Tips of the PT fibres from the wing buds