Hi MO,
Thank you very much.
Yes, the outline curves seem to cause some curve, and curvature (G1,G2), inaccuracy of some sort.
I was unaware that Inkscape did centerlines, but did briefly try Inkscape outlines. I think
Inkscape failed with an unfuzzy band (?).
Will try this "Krita".

For my particular PNG's, I think that in the overlap regions, some pixels only have one color (plus that color's fuzziness, so recovering say the blue band, will result in its tapering down to zero. So maybe some blending in MoI will be needed later.

- Brian