I often use varigated thread. It's so hard to tell without seeing them together. Sometimes what I think is perfect is a little too light or dark. It is helpful to unwrap a few feet of thread and lay it out on your quilt to test a few colors. I also recommend making a test square of leftover scraps of your fabrics to try out a few colors. I will be doing this myself soon with one that has black, yellow, orange, red, white and blue fabrics. I can't tell until I finish assembling the top. Sometimes I have a harder time picking the bobbin color! :)