Help: How to remove stain on synthetic leather cushion?

Hi Guys, i had stain my bed frame cushion by a very old faded nylon string during moving. Did not expect the string color dye had just touch the cushion surface for less than a min it became permanent on the surface. I had tried turpentine, astonish, contact cleaner, detol and kitchen cleaner also can't get rid of it. Can someone please help thanks.  :'(