I prefer a thread color for quilting that blends in as much as possible. It is tricky when you have very dark areas and light. I'll often choose a medium to light gray in that case.

Hi, welcome from North Carolina. You'll get expert advise on any questions you might have here. I agree with the medium or even light grays for the piecing, but are you asking about the quilting? Are you planning to stitch in the ditch? That's usually the way most beginners do their early quilts. ... quilting right on the seam line. It isn't really meant to be visible. Then the med.gray would blend in fine there, also. Just my opinion. The important thing is that you enjoy your project and have fun!

When in doubt, I like Superior's Bottom Line thread in silver for quilting. Here are links to it in spool & cone:
https://www.superiorthreads.com/the-...lyester-thread
https://www.superiorthreads.com/the-...e-polyester-th

This is the thread that Bob at Superior Threads (he has a number of videos on Youtube) says blends in with everything, and I have to agree. It is a great thread for a beginning quilter because "mistakes" are not so noticeable. If you use a highly contrasting thread, mistakes show more.

I am not a fan of variegated thread for quilting unless it's a special application. The problem I have with variegated is that it blends in sometimes and stands out at other times. The standing out part can be particularly distracting if it happens in an area where the quilting is not perfect.

Jamie Wallen recommends a "baby poop green" in Isacord brand thread; says it blends in with everything (I think because it is a green with a lot of gray in it). I would have to look up the color number but, honestly, I think you are better off with the silver above considering your colors are yellow and blue.

Edit: Here is a link to Jamie Wallen's website. His "baby poop" Isacord number is 0232 "seaweed".
https://quiltersapothecary.com/products/isacord-thread

That's my motto...when in doubt use Grey. :)
If you're still in doubt, try it on a piece of scrap. Piece a few pieces
of the fabrics you have in your quilt then run a length of stitches
across the whole thing. It will give you a good idea if you like it or
not.

Welcome from NE Ohio.

Welcome from VErmont

the new neutral
 

My kids tease me, because i call light grey a neutral thread. I use it for all my piecing. Top quilting threads are personal preference. I've use Superior King Tut variegated for hand quilting the top of a queen size batik quilt and i've used standard off white hand quilting thread.
Welcome to the thread. This is a great bunch of guys and gals to learn from; always someone has an answer if there is a question that needs input.

Welcome to the the QB!

One of the best things about quilting is that you can choose colors you LIKE! If you are afraid your quilting will be wobbly, pick a neutral to blend in. If you want your quilting to show choose a contrasting color. Whatever you do will be fine if it suits you.

Welcome, I hope you find many hours of joy in your quilting like most of us have. I agree with the advice you got already about laying out thread of different colors and seeing which you like better. I use invisible thread when I can't make up my mind. Good luck with your quilt.

Welcome to the board from Arkansas.