I don't thnk pressure itself would cause that effect. "Newton's Rings" are caused by light intereference from its passage through a very small and uneven space. It could be very noticeable when magnified from a negative, but I don't ever remeberr seeing it from, say, a piece of glas laid on top of a piece of printing paper.
Newton's Rings are fairly common on graphic cameras. I think that is what she is using here. The copy board on most copy cameras have a vaccuum on them. You load the image and push/pull a lever and the copy board vaccuum starts. The copy in drawn into the frame. Some of these copy boards will allow the user to draw the vaccuum and then release the vaccuum and then make the shot. I have seen this cure the Newton's Rings on several cameras in my sorted graphic arts past. The NR's sorta look like the amobias or those marks on paisley shirts. Just my 2 cents worth. As to what is causing the yellow marks, I have not a clue.