Here's the final layout, before I picked it up off the floor:
1/4 of the quilt is visible. Each small square is actually a pile of four similar squares. The center is at the lower right. Here's what it looks like now, ready to start sewing:
Here's what the layout looked like when I started - note the magenta square in the corner that stands out like a sore thumb. I had arranged the 29 color groups in a color wheel. I could have chosen any color to go in the corner, but I had one particular set of squares that separated exactly into 8 and 20 groups of four, so that set became #8 in the scheme. That gave me two choices for #9, and one of them made more sense. This made bright magenta be the #1 color. In the first picture, it repeats right next to the main diagonal, and that's great, but eventually I found some more subdued colors for the outside corners.
These are mostly scraps from other projects I've made over the years. In a few cases, the set of squares was sort of awful, so I cut some new ones from my fabric stockpile. In other cases I needed one or two more squares to match what I had, and I was able to piece together squares from two bits of 1 1/2 inch wide scraps.