I do it like this....not just a single thread, but a lot of thread pulled out and overlapping.
"Tip to help choose the color of your Quilting thread"
http://thecalicohouse.blogspot.com/2...r-of-your.html
For the back of the quilt, I usually use a blending color , nothing that contrasts too much from the backing fabric. I usually use prints for the back of my quilts, the more solid the color is, the more the quilting is going to show on the back of the quilt.