I ended up drilling it out in a attempt to drill and then remove the green part in-whole.
They have really got it put in. It's thick gauge plastic....that won't bend easily with a pick or needlenose plier.
I removed as much as I could - cleaned it up with a round rasp (and even used a coarse round rasp very carefully) as the plastic is that thick !
I'm sure I might have had better results if I was do it on the ~knuckle~ side, but I would not see a easy means of removing the head cover....and I did not want to mess with the finish that much doing any prying.
Removing these on the Grohes is a walk in the park compared to this one