I would use black and white varigated.

A steel gray would look great.

Go with grey, variegated if you can find it. A large meander would be wonderful. The quilt is beautiful and she (someday her children) will be able to use any color with it.

I would use grey.

I really like that quilt! It's very modern looking, IMO.

i think grey would look great

Well I have practiced with different colours on my practice sandwich and have tried with the following, black on its own, as someone said, really difficult to see and didn't look quite right. Then I used a varigated grey/black/white and that looked really nice on the solid black. Then I tried plain white and that certainly stood out more. In the end I have decided to go with the varigated thread on the top and plain white on the bottom of the quilt as that is the one that looks better on the back. Thank you so much for all your help and one day, when I am more experienced I hope that I can return the help. When I finally have it quilted I will post a picture.
Sue

I think RED would be gorgeous, but then I,m partial to red, LOL.

I would use a black and white variegated thread in a meander.

RED - would add a little PIZZAZ. J J