To my eye, the blue frames the blocks and draws you in, whereas the yellow just doesn't have the same sense of completion to it. If you use the yellow I would be sure to use the blue for binding.

Blue for me.

that is a hard one. blue best, but yellow is fine too.

If I were you, I'd use one color as a narrow sash (finished width 1/2" or less) and the other as the wider sash that you've already planned. I don't think it'll matter which color is used for which purpose, but I'm sure the overall effect will be much more stunning than anything you can achieve using only one fabric.

Just my humble opinion, of course.

Love this idea but I would use the blue as the sash closest to the blocks - makes them "pop" to me. just my 2 cents

Like I always ask. what is the color of the room it is to be used in or what is the person's favorite color? Actually I like the blue! with yellow corrnerstones!

Yellow :)

Another vote for blue :-)

#1 with the Blue ~

Blue