After reading the comments, I bought the exact blue of my cutting mat that several people thought was part of the quilt. And then decided not to use it.
Still not in love with anything, I went back to my original dark brown solid, thinking I could still make my original vision work.
Since I didn't like it anyway, I figured I had nothing to lose, so I cut it up into irregular strips, perpendicular to the original green columns. (Here it is randomly arranged back together.)
Then re-auditioned all the colors I tried the first time around (you know, because they worked so well originally...).
and finally, blue
I liked the blue and went with that.
Thanks to everyone who suggested cutting mat blue as an accent! :)
Here is my finished piece, a wall quilt, which measures approximately 26" x 21".
Here's a close-up of all three. I especially love the boxy one in the center and was pleasantly surprised by how good it looked in my first attempt.
Here's the back of the quilt. I have NEVER had the back of a quilt look this cool.
Have you made anything with emerald?