The problem is that the alloy parts cannot be re-anodized if the steel parts are in place. Removing the barrel is very risky on an alloy-frame, due to the risk of cracking the frame and/or the frame threads coming out with the barrel.
You will have to live with it as is, or paint it. I have had some success with "Aluma-Black," but it will not "take" if any trace of the original anodizing exists. You have nothing to lose by trying it, except a few bucks to buy the product.
Too bad, since the .32NP Couriers are scarce.
(Apologies to anyone offended by my "delivery.")