Brilliant analyses, Karin -- utterly illuminating!
Yes, the "bands" of color -- I see it in Helen, I saw something like it in Diana, and I remember seeing it in various Italian Renaissance paintings at the Norton Simon Museum as well.
My palette is very similar to yours (although I dropped a cool yellow, since the only greens I've painted are for foliage, which in nature is almost always of a low to moderate chroma -- any red in my warm yellow only serves to subdue the green)...
http://www.douglasdrenkow.com/page17.html
In addition, with earth shades, I feel like Jim does for all specialized colors -- the wider variety at hand the happier I am.
And I envy your visiting La Gioconda in person -- I've only seen reproductions, invariably yellowed.
Thank you for sharing so much with me (and for putting up with my being so very opinionated, by nature)! It was an honor exchanging views with someone as accomplished as you and Jim.
I must retreat to the easel -- a gallery beckons!