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