Do you just have the six blocks?
Take all your blocks, including the purple ones that you think you don't like .... to your LQS and audition fabrics.
I think you could find a nice print that would have all the colours, and tie them together. Also, watch for a multi-coloured narrowish stripe that would blend. And perhaps another solid plain, black? Then use them to sash and/or for the blocks between.
If you have enough, I probably wouldn't use the layout as you have it, but rather stagger them, with the sashing between.