Thanks, Susan.
From the previous, I'd definitely disagree with Rita
and say that the blue Chionodoxa is highly invasive (at least in my experience with maintaining several perennial gardens in which I had planted it).
Still, it all depends on what you call invasive, on the growing conditions that lead to something being invasive and on what garden effect you want.
The reason that the blue Chionodoxa spreads (here, at least) so vigorously is its prolific seeding.
Personally, I'd say that one mark of an invasive plant is that it doesn't just stay in the property of the person who planted it, but it goes into the neighbour's property .
I've seen this plant over 15 or so years. It's aggressiveness makes me also wonder if there's going to eventually be local ecological concerns with it.