I wish there was an easy answer to this for you....but the fact is, each hairpiece is individual and will take color differently, not only from your own hair, but from the hairpiece you had last time.
to be safe, apply the colorant to a comb and comb it through a small area, let it process and make sure its the color you want. if it is, then proceed with combing it through the rest of the unit or your own hair or both.
hope this helps. a lot of this is trial and error unfortunately...that is why its best to do a test area first.
DebbieS.