I love the quilt, looks great,
I agree with someone above who said it doesnt need a border, just quilt it and slap a binding on
piece the binding from strips in the quilt
Now if you want a border, here is what I would do,
1. I would put a 1.5in border (cut at 2ins) of snow white (it is softer color than stark white)
2. then I would make piano key border out of the fabrics from the interior, so do the 3 pink fabrics, 3 blue fabrics, 3 green fabrics, 3 pink fabrics..etc. Cut them 2.5in x 4.5 ins, that will make a 4in border and match the "rectangle" look of the interior.
3. Bind with the snow white from the inner border, this will frame out the whole quilt.
Hugs!