Sight unseen, my suggestion would be to square each block, find a contrasting color to sash it all around, then keep each set together. When you have enough block sets to make your quilt, then sash each block to the best choice to finish to the size which will work -- lets say 12" == Basically make a square within a square, all to finish the same size. Now you can just sew them together, or add a neutral color to create an additional sashing (with cornerstones?) and border too. This should avoid color washout and provide uniform sized blocks, while maintaining each block's individual appearance.