I was reading some posts about hair dye questions and since I'm a licensed hair stylist thought i'd help!
Yes - Ferria does contain metallic salts which makes it VERY hard to get rid of! I suggest getting a malibu treatment (you can buy malibu packets at sallys - leave it on for at least 45 minutes) then color over it (you can only go darker - either your natural or darker).
For manic panic like colors that are more permanent I like Special Effects (online or some hot topics), Paul Mitchell (online) it's called Ink Works and is my favorite! I use it on my hair. Or color zone (sallys) or Rusk (online).
Hope this helps!!