I’d re-think installing hardwood floors in gray tones. The faux-gray wood floor look has passed. One of the reasons the look passed so quickly is because it is so hard to match anything with faux-gray hardwood. Not just floor registers, but also sofas, chairs, wall colors, draperies. Get a natural wood color hardwood, and there are floor registers to match. In fact, many flooring companies offer them to match their flooring.

I painted my registers with Rustoleum Satin Nickel spray paint. They were an ugly green brown color that didn't work with the gray toned, stone look LVT tile I installed.

I didn't want to buy new as I am renovating an old home and had lots of expenses and this was a place I could save a few pennies. They have held up perfectly. A few had some rust spots so I primed first with Rustoleum Rust converter and then painted. Painted the returns and the screw heads on the returns as well.

https://www.homedepot.com/p/Rust-Oleum-Universal-11-oz-All-Surface-Metallic-Satin-Nickel-Spray-Paint-and-Primer-in-One-342508/307244958