From what Mike has said, nobody is doing the phosphating as was done contemporary to the original production, so everything is a little darker. You can take the door off and hit it with some naval jelly/rust remover and it will take the blacking off. You might have to do a couple of applications to get it right. I don't know this, but it seems that Brownells and H&R/PSA get their stock at about the same time, so possibly/probably the same supplier.
The slip ring should be a lighter gray or at least not black, but here you're back to the often discussed 50 shades of gray that goes with anodizing. You can find original Colt slip rings, and there are some examples of H&R's slip rings that have the more widely accepted lighter shade.
You can also hit your black/darker gray LPK parts with the naval jelly, or at least the visible ends if you wanted to do that. And somebody somewhere at some time might take exception to a black ejection port door spring. I've seen some guys post about giving that the same treatment. I had a few bright springs in my spares so I just switched that out.
All part of the fun of cloning.
You have a good looking rifle, regardless. This one and your 177.