There are three different variants of this uniform:
Orange and gray variant typically worn by Brotherhood power armor users and recon forces.
Olive and black variant typically worn by Brotherhood ground troops, paladins or knights with combat armor.
Jet black officer variant (named "BOS Officer Uniform") is worn only by Paladin Brandis during certain quests.
The BOS uniform allows armor pieces to be worn over it, but it may not be modified at a workbench. All three variants have the same defensive stats, weight and value.
The bomber jacket is a separate piece of armor that consists of the orange uniform with a brown leather jacket.
In the Art of Fallout 4, the BoS uniform is described as being designed to have a variety of hard points and attachments for interfacing with a power armor frame, though it is not necessary for using power armor.
This armor has an associated headwear item, the BOS hood. During the intro cinematic, one can see a power armored soldier wearing the BOS hood while he receives repairs with his helmet off, which points to the new BOS uniform being pre-War 'under-armor' for power armor frames, akin to the recon armor from Fallout 3.
