Mismarks & other odd markings in Labradors part 2 - Woodhaven Labradors
If you look at "Other" in the link above there is a greying factor. There is a photo of grey appearing in a black dog's coat, under the heading "White Flecks." I can see your photos, and can especially see the grey in your last two photos. But not well enough to see if it looks like the link.
ETA: Weird, now I can't see your photos.