I think that a Disappearing 9 Patch would be great. You can use your blue/purple as the corner pieces in your 9 patch, and the coordinating colors as the other 5 squares. When finished, it would look as if your blue/purple would be framed by the other fabric.
It's a really versatile pattern. I've seen whole quilts made out of 2 fabrics. I've made them using 3. Then, I've seen them on this board set up as I Spy or Charm quilts with each corner piece in the 9 patch being different from all the others.