Hi Sarah,
Yes you can use colored thread to quilt it, however dark colored thread on white fabric is very unforgiving in showing mistakes. The lighter in value you go with the colored thread the less any mistakes would show. You can FMQ your blocks heavily with colored thread and it will definitely give the appearance of adding color to your light blocks. Here is a pic of example showing FMQ of a very light colored thread on black fabric to give you an idea
yellow green thread on black
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