When I sew a scrappy binding I use variegated thread.

I use a lot of the neutrals - taupe, grey, deep cream. They tend to blend into most everything. When working with things that are mostly dark, I often use a charcoal, a navy or a chocolate. They are not as stark as black.

I agree with klswift.

Your quilt is really pretty. I love the colors. I would choose a white or off white for the thread, since the background on your prints is light. Once the quilt is laundered, the stitches will be much less noticeable. Don't sweat it... just move on and start your next quilt!