If it were mine and I was using one color only, I'd match or go just slightly darker than the background. I don't mind how the light threads usually look fine on the prints, but I don't often care for the dark color thread on the light background.
Do you have some threads you can unwrap several feet and put on top to see how it looks? It's a good way to gauge it. I like to take pics too. For some reason, when I see the pics, it helps me decide.