My first attempt at visible mending, tried Sashiko. It’s hard to tell but the thread gradients through lighter and darker shades of blue/teal.

[u/LyraAraPeverellBlack]

[u/sezit]

Nice! I would suggest taking black thread and whip stitching to the patch all the way around the hole. You don't want the loose fabric to snag, or the edge to fray from wearing and washing.