that's the ex color for ferry, which is only obtainable if you transfer a save file from gbvs with the ex colors on it already. iirc, the ex color was only obtainable from attendance in at least one online tournament that the gbvs dev team organized.
I obviously believe Nier is broken beyond belief, but as I ferry I don't mind this mu at all. You can force Nier to make very hard decisions super easily.