I pretty much stay with neutral colors (natural, white, medium grey) for lighter fabric and use (black, Persian blue, or the medium grey) for darker fabrics. I like to keep multiple bobbins made up and I really don't want to need to have a trillion bobbins with multiple colors I would rarely use. Surprisingly, I found that the neutral colors, seem to blend in and take a hue from the fabric it is next to.
I go with what blends in with the backing fabric for my final quilting.