Did you try Gel Coat Products? I've had good luck with them for odd colors.
My experience has been that new gel coat blends in nicely with the existing, faded gel coat. After your new gel coat has set, you will smooth it with progressively finer sandpaper. This will take off the older gel coat around the scratch.
Be sure to go over the entire area with a buffer and compound. After waxing you will be surprised as to how well the repair blends.
2006 Bayliner BR205
A1 Gen 2 1.47
5.0 carb engine