at first i wondered about that, too. ( xing sent me the model + his skinfiles ) - but then... the osiris is darker, too. - its more a dark, satin grey than a shiny silvery metal. - the dreadnaught is not cloakable - and does not possess the technology to offer a small radar image.
the osiris on the other hand is not only supposed to be totally cloakable, but also offers reduced image when not cloaked.
the carrier, as i understand it is / was a further project of libery. it combines the need of a flagship with the technology to cloak and offer a small image on enemy radars. - its hull is rather that of the osiris than that of the dreadnaught - so its darker.
but its still strange. - when you fly that thing through liberty, it looks as if someone tried to hide an elephant in a crowded street. - that ship is so big, .. ( and visible from westpoint when it is actually in manhatten orbit ) - that offering a small image on the radar is like totally pointless.
but its cloakable, too - ( in RP ) - it has those little arcs on its back.... well. it looks libertyish - but yes, it stands out when next to the rest of the liberty fleet. ( but then, i don t think there ll be many of those )