Hmm, I usually use bright red Aurifil (have about 30 spools of it) to piece unless I'm sewing white fabric. I have never been able to see the stitching thread in the seams from piecing. When I first started quilting, the quilt magazines then had long detailed articles and one article explained why red was a great neutral to use for piecing different color fabrics. And it's fun to have red thread on my machine. Makes others to HUH?