Hi Drew,
It can correct a color mismatch within reasonable limits. You put the color blender on a comb and comb the area where you own hair and the hair system meet. The color blender is applied to both. And as the name says, it blends the colors of the two together. You're not going to blend, say, a jet black hair piece with your own medium brown hair because they're just too far apart and it wouldn't look natural. But if you've been out in the summer sun and your hair system is losing some of it's color the blender is just the ticket to even out the color differences.
Regards,
John