Something's taken the dye out of my jacket

got something dripped onto my black jacket going into a tube station, god knows what it was.

where it's been on the jacket is now what looks like water marks, but i think it's the dye being taken out.

it's black and a bit of a run around jacket, nothing too smart, but i do really like it

is there such a thing as something i can put on myself to re-dye that bit of it? or could i get away with a black permanent pen?

thank jet, knew there was something better than a marker