You have to be a bit careful.
If you lighten your piece & your natural hair, the colour may be lighter, but the shades could be completely different and its likely there will be heavy red tones to the piece.

There is another product thats more gentle called Goldwell System Color Remover available on eBay.

Whatever you use, PLEASE do a strand test first on all types of hair to gage what the results will be & how long to leave it on for.
Otherwise you'll get in a vicious cycle of lightening & redying that will kill your piece.