And, so, I frogged it. It's interesting--I've put together quite a few afghans, and had no trouble with the color. But, I think the main difference was that I started from scratch, in the yarn store, saying "I need 3 colors." Starting from stash, and wanting as many colors as I could find? Well, I went a bit wacko, and it showed.
Here is my newly-frogged ripple. The yarn balls on the left are the two colors that really killed it. They are going totally away. They were too muted/frosty, for what should really be a mix of spring/warm/clear tones. I didn't like the Caron Light Country Blue from the moment I got it home, but my Random Color Picker insisted, so I went for it. The peach I will discuss below. On the right are (some of) the colors that will go back, in a slightly different order, plus the skein of lt. coral that will replace the peach:

Here is what I am still mulling. I went earlier today and found this light coral yarn. It is very similar in shade to the other yarn (which is a higher grade acrylic--Unger Utopia--that I borrowed from another project). However, when I lay the coral on top of the afghan-in-progress, it sparkles. The peach yarn just sits there, looking boring.
The light is a bit different in these photos, but you can still see how the Utopia looks in the granny square--nice contrast, and it appears as a
dark orangy peach. I guess if I've learned anything from this process it's that the more color you work with, the trickier it becomes to keep the project, as a whole, in focus. You can very easily end up with a glaring mistake that doesn't show up until it becomes part of that whole. So, then, you rip, rip, rip-it. :)