The only reason you would want to use the same color thread as your backing is to camoflauge your quilting, to hide mistakes, etc. Prints will also do this no matter what color is in your bobbin and solids tend to show the quilting even if you match the color. If you are confident in your quilting I say ignore your backing color and go with whatever you have in the top.
I have had client quilts where the client specifically asked me to match the back and then later regretted their choice because you really couldn't see the quilting. Given a preference I like to match my bobbin thread to my top thread and ignore the backing color. Some of the results have been spectacular, like red and white bobbin thread on a black backing, made the back almost like a whole cloth.