I don't know much about MC or computers, but as far as I understand each bit has both blocks, shift up for blue=0, shift down for green=1. Here: http://i.imgur.com/rqZm4DU.gif
Yes, but you don't see BOTH block types on the big tape. Swapping bits requires one block for each state, but the green ones are missing from the tape screenshots.
I don't think that they have to necessarily be green. So the fact that you don't see them may not mean that they are not there. He may be using blocks the same color as the structure for aesthetic purposes.
