I have the exact same granite as you! The exact same. I too have noticed this colour in my slab... however, mine are very, very small specks. So small that you have to actually look for them and there is only about 5 specks in total.
Mine has more streaks of that purple/black. It's really nice.
That spot looks pretty big though. Why they even used that piece of the slab is weird. I'd definitely say something about it.
As to how to get them out?... I would think they would have sealed over it already. Rock is porous so once its stained is pretty well screwed. That's why they seal it so liquid doesn't actually get into the rock.
Looking around
Wondering what became
Of what I once knew