I try to avoid using monofilament simply because it's such a pain to use. You have to loosen the tension all the way. I agree with the recommendation of using Bottom Line. With the color scheme you describe, I'd go with natural.
Oh, I just had another thought! Bottom Line is 60 wt, which is fairly fine. Microquilter is 100 wt,
really fine. You can get both of them on Superior's website.
https://www.superiorthreads.com/thread/microquilter