So far, I prefer the radiants and Namtam's EW Asscher combo best. After whittling ideas down to just a few, in the end, I have a feeling that the setting, both in terms if its color AND design, may dictate the final choice.
Interesting thought, DJM, regarding the soft yellow color vs. high-white. Blue and yellow are not opposites on the color wheel (that would be blue and orange), but they are far enough apart to lend some support to your theory about how the yellow color makes the blue pop. My only concern is that, for me anyway, the yellow color "gets in the way" of the blue. Yellow is one of the most highly visible colors (actually, I believe it IS the most visible, unless you get into the neons), and it tends to advance forward (hence its prolific use in signage and other "need-to-see" items). By contrast, generally, blue is perceived as a receding color. So, I may prefer a blue/yellow combo when the yellow is the focus (in the middle) and two blues are side accents. Make sense?
Regardless, I'm looking forward to seeing some examples of high-color stones and contrasting the two effects: high-white sides vs. tinted sides.
Now here's a thought: It may be, if the entire piece will be done in yellow gold, that the tinted white looks better overall because it will blend with the ring, as opposed to introducing another perceived color... Better still, perhaps dropping down to the U-V or W-X colors for sides, to introduce a soft "golden" looking pair (careful, not yellow) will work... kind of a warm neutral that disappears into skin tones and yellow gold, to contrast with the cool blue.
So, basically, I just theorized about how "yellow" may not work, and, then, I ended up suggesting "gold," a complex form of yellow as a solution... I'm an idiot.