Hi again, haha.
Yes i get these from time to time. They are prominent when i blink or focus. They turn from black to white depending on the surface. More often they are white for me. Like a spot in my vision that i can't see unless i move my eyes or blink/stare.
They are odd! Do you have migraine auras? - I do, i've often wondered if they cause them. I have all sorts of visual disturbances from time to time. Have done for... as long as i can remember!
Message me if you need to chat about them. I know they can be scary - believe me!