DOTTYMO

I'm with kristijoy about varigated . If it was me I would stabilise in the ditch around the square and border. Then I would put a flower shape corner to corner curves with walking foot in each square an easy feather or similiar in the background.

I don't like to see an all over pattern going across a wonderful patchwork top and distracting from the pattern.
I use same colour thread top to bottom as this prevents any not fine stitches not showing as much.

MagaQuilt

As with most things it is a matter of taste. The idea of pooling the threads you think of trying is very good - I use that. I also like to make up a scarp block of the fabrics I have used in the quilt, sandwich it and try the patterns I want to quilt with the thread I think I have settled for when pooling the thread. That way you will know how it looks on the quilt. I prefer that to unpick because I don't like how it looks.
It is a lovely quilt so take your time in deciding on thread and quilt pattern you want to use.
MagaQuilt

Rose S.

I love King Tut variegated. They have some wonderful colors and I can almost always find something I like. I don't think the blue would look bad on the lavender. From what I can see of the quilt, there is not a lot of lavender. However, not sure how I would feel about it on the white parts of the quilt. It would depend on how dark the blue range went. If the darkest part of a variegated blue thread was very dark, I would not like it.The best advice is that already mentioned....pull off a few feet of thread from the spools considered and let it fall on the quilt and see if you like it.

PatPitter

I would consider doing something other than meander/stipple over the whole quilt. As others have said, stitch-in-the-ditch around the squares. Maybe do stipple in the unicorn squares with a dark thread and then stipple in the white squares with white thread. It will require more stopping and starting but I think it will look better.

Or consider a diagonal grid of straight line stitching.

Sandygirl

I always tell my long arm quilter that I dont want to see the thread. I want to see the fabric. Her choice on the color of thread.

Sandy

JENNR8R

I solve this problem by only using clear YLI monofiliment thread. I don't want to see a thread color, just texture. I use it for all of my quilt tops.

paoberle

Practice on some scraps with differ t colors and see which ones you like best.

ManiacQuilter2

I am sorry but I prefer stitching in the ditch with the BQ patterns to make the piecing pop. I would see what thread would match for your focus fabric and meander in That area. Nothing is going to look good with any thread meandering thru dark purple and an ecru background. I don't prefer when you have such beautiful pieced quilt top to be distracted with thread going thru the piecing. he is how I quilted a BQ2 quilt. I did straight lines that I drew that fit in the brown background. I try to make the quilting merger in with the quilt. I wish you good luck with your choice.

Ariannaquilts

Belfrybat I just wanted to make a clarification about what you said "FMQ = sewing machine not longarm" that is not correct you most certainly can do FMQ on a longarm.

purplefiend

I use variegated thread quite often, I also quilt with a domestic sewing machine. King Tut threads by Superior is my favorite, also use YLI variegated threads.
Sharon