I think it depends on your fmq skills. If you do the white thread on the maroon fabric the fmq will show up up quite a bit. My fmq is "OK", but not great, so I would use white thread on the squares, crossing over from one to another with a slow fmq stitch in the ditch between the corner squares of each block and the sashing. Then I'd use maroon thread on the maroon fabric. I always try to match top thread and bobbin thread and since it's a wall hanging there won't be a lot a people checking out the back.