When I piece, I use everything, because it never shows in the end. When I quilt...I often use different colors...If I am quilting over dark green leaves and want them highlighted, I will use a green, same with sky, etc....if you are asking about running out of thread, and quilting with the same color for most of it, been there, too...you can get a color close to what you're using and no one will be the wiser.