There are so many options! I personally would prefer to go with a light background / sashing, but that’s a personal choice. I don’t have the best eye for colour so I wouldn’t dare to use a more unusual colour. I think @Edel has made quite a few scrappy quilts in (to my eyes) unusual colour combinations so I’d look those up for inspiration.
One project I made recently with (full-sized) charm squares is Rainbow charm baby quilt - Inspired-along challenge 2022 Entry After lots of playing around with the squares I decided to do it in colour order. These fabrics all matched but I still went with white as a background colour to make it a bit more easy on the eye.
But here’s an adventurous person who went for a scrappy look and a non-white background: https://cdn.shopify.com/s/files/1/0091/7061/6401/products/11176_056_D1_1024x1024@2x.jpg?v=1569162104 It can work but you just need to be very careful picking the fabric. I would guess navy is indeed a bit too dark for your squares, but as I said, I don’t really have an eye for colour. Or if you’re going dark, maybe go really dark and go for a near-black or dark grey fabric.
I also saved this quilt but personally I would think that would be a bit too colourful: Nancy Zieman The Blog - Quilt to Give: Step Seven—Audition Borders I still saved it just because I’m trying to force myself to go for more non-standard combinations.