Oops, I did not mean to infer that I
knew it was open cell foam. I do not know one way or the other, I am just not willing to chance it. I'm editing the post to make that clear, thanks for pointing this out.
This is what I {think I} know. When the foam guys came out to spray the garage / workshop project walls {just the downstairs part has been foamed so far}, I asked them how I could tell that they were spraying the closed cell foam I was paying for, besides me looking at the barrel the hoses were connected to. I like his answer. He took a piece of trimmed foam {it was a different color from what he sprayed for me}, handed it to me saying it was open cell foam. The open and closed cell distinction is the amount and size of any air pockets in the foam. He asked me to mash on it, or squeeze it. I did and found it fairly soft/pliable. Then he asked me to mash or squeeze the foam he sprayed on my walls. They had already trimmed a couple of places that were too deep for the 2x6 cavity and I found that piece was more firm than the one he gave me at first.
That said, the areas I used Great Stuff to fill in over the windows and side door felt like open cell foam to me. There are several varieties of Great Stuff in stores. One said "big gap filler" while another says "minimal expansion." AFAIK, they don't say open or closed cell on the can, but if they did, I missed it when I read the label.