I have done a couple of quilts with similar colors, black background. I used black thread and for yours I would stitch in the ditch around the colored triangles. I did a kind of spiral but it was squared rather than a circle, if that makes sense.
Honestly, the quilting didn't show up a lot, but still I liked it. I didn't really want the quilting to be the "star of the show".
Your quilt is really nice. I love the brights on the black.
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