It is permanent (or can be semi if left on < 15 min or so) but because it does not lift your natural color, there is no line.

It's best to choose a color 2-3 shades lighter than you think would match, esp at first since your hair will be porous from the old color and could go too dark. I'm pretty good at helping choose colors if you need help. You can post/send pics or just tell me which shade(s) is closest to your own, or what you would like.

SF Bay Area, CA * "The Angel-Goddess-Guru of Haircoloring"
3b/c/a mix. medium texture, low porosity
My Motto: Strand Test! some hair pics
-- gone, but never forgotten.