Beautiful picture !
Why do they wear a blue scapular ?
I do not see a scapular at all. The blue garment looks more like a full apron that is worn over the black habit. Do you notice the bib? That bib is similar to what the Mennonite women wear over the front of their dress.
Of course, I could be wrong. When I was in a monastery, we wore a scapular, a rectangular piece of fabric, and it was free flowing, not tied at the waist. Furthermore, the scapular did not have any pockets.