Then at a minimum only milspec anodizing will do. And most companies selling AR use that and say they do.
It's a distinctive finish different than aluminum storefront (which is good) or decorative import knife handles (like on cheap folding box knives.) It is an art to apply, even tho most of the process is well known and controlled. Nonetheless electricity and chemicals are used, dyes saturate the finish, and different alloys react uniquely.
Very few makers get thrown under the bus on the subject. Even issue Colt, FN, and Remington contract rifles may have finish differences upper vs lower, and the milspec allows it, as it is just a cosmetic issue, not a functional one.
Run a 10 year old rifle thru ten basic training cycles and they ALL will degrade. So do the M9 Berettas.
If someone is looking for a perfectly matched upper and lower in a presentation grade finish, a request to the maker of choice might be the better avenue. Otherwise, next months upper won't likely match last summers lower and the industry cannot and will not guarantee it. And again - it's not a military contract requirement.
If anything, some of us would like see makers stop using black at all. It's not original nor is it effective as a concealing color. While the OP might not want to see any makers thrown under the bus, some of us might because we can't seem to get anything but black on the lower priced items.
Oh well, where's the Clorox.