I already know that I want to use a white for the sashing on my Scrappy Paintbox Quilt. I liked the way it looked on my first Paintbox Quilt and I think it's the best way to show off all the beautiful colors.
When choosing a white solid, remember that you don't have to be literal. Many off-whites, creams and ivory solids are available. Look at the prints you'll be using in your quilt. Do they include white? If so, is it mostly bright-white or cream? Take scraps to the fabric store with you and hold them up to different white solids. You might be surprised at how much better they look on a less-bleached white.
For my Scrappy Paintbox Quilt, I chose Essex cotton/linen in White. The photo above shows some pieces from my quilt on fan favorite, Kona Snow.
If you're following the Paintbox pattern exactly, you'll actually need two neutral solids. One is for the front sashing and half of the back and the other is for the second half of the back. (You can see a graphic of the quilt back here.)
The background in the photo above is Kona Stone, which I like. It's definitely a front-runner for the second half of the back!
When I'm choosing neutral solids, I generally try to stick with the more gray/tan and less greenish colors. Kona Stone is a favorite and is similar to Essex Putty.
Oh, my! I don't think Kona Black is the right choice. Too bright. Too dated. Too much!
Much better! Kona Charcoal is much easier on the eye (and wouldn't be as much of a cat hair magnet).