I just went in search of the name for the block and stumbled on this quilt, where the block is called X block. (On EQ7 is it called 4 X). Anyway, notice that the quilter used all different colors of sashing, and it is beautiful. Her layout is a little different in that the same fabric is used on either side of the sashing, but I don't think that is necessary for the different colors of sashing to look good.
http://home-and-garden.webshots.com/...01712405OnFBNX