The barrel is steel and is parkerized.
The upper and lower are aluminum, and they are anodized.
There is often some variation between the two. Different materials, different coatings makes it tough to match.
If the upper and lower weren't finished in the same batch, they can vary.
Your best bet is to take a black rag and soak some CLP into it. Wipe down the whole gun. Now take a look at the finishes and see how they look.