For a batik, I'd go with something that had the blue in it & then either purple or green -- or both.
For blender squares, I guess it depends what you're hoping to have as your finished look. Yellow would make for a cheerful country quilt. You could stick with the white & create a traditional Blue & White quilt. You could pick grey for an understated look, or a bright red/green/purple for a vibrant contemporary looking quilt (even if you are using a traditional pattern).