I normally use the same color thread top and bottom as I don't feel apted enough to know how to tweak the tension so I don't get those pokies. A quilt I just finished about a month or so ago I was lucky enough that the same color worked for both sides but I had a cream colored pieced sashing before the large outer border that I didn't want to use the brown thread on so went with the cream on both sides. I like my backs to make a statement as well as the front side. The couple that received this quilt can't make up their minds which side they like best so I guess I do good this time. Here's a pic of my quilt. Can't see the cream thread on the backside but its all those little 3" triangles around the quilt, all 296 of them. What was I thinking???