I would wash the orange fabric you bought and then decide. They may have put a lot of sizing in it that will wash out so it feels softer. Also it may shrink a bit, and it may not be color fast....so I would toss it in the washer and dryer, see how it looks and feels and then decide. I have bought fabric that I have done that to...some turns out...some I toss...one red batik I bought bled every time I washed it and I washed it three times. I ended up putting it in a garage sale with a note on it "not colorfast" and a price that was about 10% of what I paid for it. I usually just use quilting cotton for the backing....but I am not a matchy type person so what I often do is look at the clearance/sale section of the quilt shop and if I see a fabric with enough yardage that tickles my fancy...I will buy it even if I don't have a top yet for it. So I have a stash now of potential quilt backings and mostly I have been satisfied with one that will work and even a few times where it was amazing how good it looked. I especially like to keep my eye open for flannel material that would work as a backing as my family loves flannel even if it is just on the back of the quilt. I just can't pay full price for flannel for a backing for a queen or king sized quilt.