Black Noir is black in the comics. The creators have designed the character in such a way to give a specific look and feel, and the black complexion is an integral part of that design.
Obviously, the main characters are the two Deadpools. They are both versions of the same character but with potentially different backstories and personalities in this graphic novel.
Well, one key point is the battle between the two Deadpools. They likely have different motives or versions of themselves that lead to the fight. Maybe one is from an alternate universe.