I use gray for piecing unless the backgound is black or white. Then I use black or white. It saves buying a lot of different colors. If I'm doing top stitching I may need to buy something to match. Then of course there are all the differnt colors of embroidery thread that I have to buy. My husband bought me a thread chest full of embroidery threads last year for Christmas. Actually that is now two years ago Christmas, with this being 2011.