QuiltingVagabond, that was a lovely idea to vary the sashing color. Congratulations on finishing your top!
I agree that this is one of the more difficult BH mysteries. I think the pieces were smallest overall of the four mysteries I've done, and there is so much matching to be done when dealing with that sashing. I am hoping to complete my longest sashing row today, and then it will be downhill the rest of the way!
I ended up doing two sets of those pesky parallelograms, the first one using the drawing lines method, which took forever. They were pretty accurate though. The second time, I used the 'Bonnie' method, cutting the parallelograms with the folded corners ruler and the triangles with the Easy Angle. That was much faster; they were wonkier, but so far I haven't had trouble using them.