In my original post, I photographed all three of these in our yard and all three were comparable in size but the one in the most sun had the very purple color.
Two of the three are growing slowly. The one that was purple has reverted to green. It appears that these favor bright light with only partial sun, this one that is at least double the size of the others.
The lower leaf on the left has been removed and I used it as an imprint for a large concrete stepping stone (we used about 130 lbs) to be used in our path around the back yard. (more on that later)