Just the cover lid edge, no more, no less?
Well, it’s aluminum. There are several options. Depending on how easy you want, how durable you want / how rough you are with your laptop, how much you want to spend. Paint is still an easy option, though it can wear, especially if you’re rough with your stuff. Home anodizing. 3rd party anodizing. Any anodizing should be much more wear resistant than paint. There is also powder coating. Here is someone who had power coating done, Making The Framework Laptop 16 Black (Project Blackwork Part 1). Seems like a lot more work than other options.
Personally, I’d go for home anodizing. For how to do it, there are tons of tutorials and youtube videos. You’ll also want to look up anodization masking, as you will need to mask off / seal off the magnets, plus the back if you don’t want that colored. And any other non-aluminum metal. Not sure if the newer CNC lids have any other metal parts.