I honestly don't know how to remove it, if its on the underside of the base, you could try bleaching it out with 40 vol. peroxide developer???? ANY base will stain if you get dark hair color on it. i can't imagine that a hair replacement stylist didn't know this. This has been talked about on this forum for years......when coloring ANY hairpiece, you must apply the colorant to a comb and comb it through the hair in small sections....even this way, some color is apt to leak down and get on the base...so you must be very careful.
I'm sorry this happened to you.
DebbieS.