What are you using for backing fabric. If a solid fabric, maybe you want to fmq from the back side, so you can see where you're going. As for thread color, I'd try some experiments on some samples first, to see what you like. Do you want the thread color to contrast or blend in? I do agree with what someone else said, using a curvy line design since the blocks are all straight lines. Whatever you decide, it should probably be something rather simple so it doesn't take away from the complexity of the pieced blocks.