Marks on denim when washed

[Im a BusyBee]

i washed my sons expensive D + G jeans in the washing machine and when i got them off the line i notice a big patch of what looks like dark blue ink (maybe colour run?) i have no idea what it is or how it got there. Anyway he very upset with me, just wondered if anyone can give me any suggestions as to how i may try to remove it?

[dancecaller]

Complain to the shop. If the dye has run they should compensate or advise you