I would have been tempted to cut them a bit smaller which would have given you a better color difference, but it is a learning process, your difference will just be a bit more subtle, I do see it, the one in the top left is much darker than the one on the top right, once you get more of them sewn and start laying them out, stand back and it will be more obvious, it is amazing just loosing the seam allowance can do to some of them as well, it is all about over all value when it is done,
the borders are all easy as they are all straight seams in the end,