A few days ago I went to get a red-on-white print to round out my red and white triangle quilt, and a selection of solids to go with the other two. I ended up with a decent election, and when laying them out in rainbow form for one of the quilts, I saw that I had two options for transitioning from green to blue. I like both, but it just doesn't work with both. The solution was to use both, but separately.
Since I needed two rainbow strips, each with seven colours, I simply made sure that each one overlapped the blue/green spectrum, and here are the two sets, ready to go into the quilt. These will go with triangles cut from a set of 20 Amy Butler Charm half-metre cuts I got a while back.
Below are the pieces for the other triangles quilt (using Kitty Yoshida's Prospect Park range) set out in piles ready to piece into strips. I'm not sure how well the gradations of each strip will show once pieced, but I can always enhance the effect with the quilting.