So I decided to ice-dye a fabric for the back. I started with white PFD cotton and soaked it in a soda ash/water solution. I squished it lengthwise and put it in the bottom of a large bucket. Then I covered the fabric with several layers of ice cubes. Procion MX dye powders were sprinkled on top. I used Olive Green, Lemon/Lime and Wine. I was trying to emulate the colors in the top. I left it overnight until the ice cubes had melted and proceed to wash the fabric in hot water with Synthropol.
It's not a perfect match. I didn't get those bright orangey reds or blacks, but I did get the soft greens and the pinks. I still think it's very interesting and the colors are close enough and I will use it.