The question has been asked many time about how to choose coordinating colors. My answer is simple...
1) What colors do you like? What do you want to make your main color?
2) Find beautiful (to you) photos and study the color. I love landscape photos. Nature is so vivid, every season brings something different. I've taken so many pictures of the farm, I often pull those up for inspiration.
3) What other colors do you see? Does your quilt pattern require light or dark colors? When you're studying the picture find those. If you love your picture, but it isn't giving you enough color variations, sit it aside for future inspiration.