Very pretty!!
I would want to quilt it so the secondary design stands out.
SITD around the all the colored squares and diamonds (large and small). Depending on the size of the large colored squares and the type of batting you are using, I might put a single circle inside that square.
If you want denser quilting that will make the colored squares REALLY stand out, finish by doing a small to medium meander in all the white areas.
OR you can do just the opposite and densely quilt (after SITD) all the colored areas and leave the white criss-cross un-quilted (except for the ditch work), and that will make the white stand out. I think this will highlight the secondary pattern the best.