Use of a mordant is necessary. I prefer using a cup of White Vinegar in the sink that has as water as hot as your hands can stand it for my rinse.
This is done after washing, in again as hot as your hands can handle, with a squirt of dawn dish soap. When you heat your dye water do not boil it. Boiling water will damage your stems on hackle. I also find that if you pluck several hackles and dye then rather than dye an entire skin, works best and saves money. Lady Clairol, used to dye hair works well and it is more of a cold dye than hot. Might talk with your wife's hair dresser to ask which colors might work for the color you need. These ladies are experts on dying hair. Why not for our precious hackle? Mary Detee put me onto using this for dying hackle. She uses it to get the exact color she needs for thousands of flies, same shade, needing an exact color. ie: her shade of dun.

To dye black: it is a two stage dye job. First clean, rinse, dye Orange. Dry partially then dye black. This is for both hackle and hair (Buck Tails & deer hair.