I agree, a photo would really help, but based on the information you've given ...
if you don't want your quilting to show a lot, I'd probably go with a grey in a 50wt
if you want your quilting to barely show, go with a muted variegated thread that is not an exact match for any of your fabrics (or else it can look like you forgot to quilt part that part)
if you really want to show off your quilting, go with a 28 or 40wt and a beige everywhere but only outline the stars. Use a red inside the stars (it won't show on the back, but you will still see the stars' outline & that should look nice).