For hand quilting I always used the same color thread throughout but I have used a variegated thread that was high contrast to the main background fabric. I was very pleased with the result:
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Now that I quilt on a LA I won't hesitate to use different color threads. some I want to stand out, others I want to blend in. So far I am always happy with the result. Here is my best example of using high contrast threads and lots of them in machine quilting. Of course, some of this is almost at the level of thread painting but it still gives you an idea of how many different colors of thread can be used to enhance the quilt and draw attention to the quilting while also complimenting the piecing.
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