Yoke stapled on to be sewn in place.
The two back pieces sewn together, showing the outside and the inside, with the yoke sewn on.
The two back pieces sewn together, showing the outside and the inside, with the shoulder straps attached to the yoke.
Since what I make are essentially just prototypes, I may want to go back at some point and make revisions. Partially deconstruct it, take parts out, add other parts, etc. So to that end I usually do sections in different coloured thread to help me distinguish what is what. If the thread is to be visible I usually use a matching colour. But for anything that will be hidden, different colour thread helps if I need to revise or fix at some point down the way. Not to mention that black on black kinda sucks. White on black is just easier to deal with.