Tarkin's uni is darker than others. More a German green-grey (Paul can either back me up on that, or completely **** on me), and others have that, but I think Bast's outfit is more the grey than the green... Which is really weird.
If Hasbro ever did a simple, plain, Imperial Officer with a relatively generic rank, I think it'd be great to see it come in many flavors, kind of like Clones. Grey/Navy or "Fleet", Green-grey (Olive)/Army or Grand Moff's(?), White tunic w/black trousers/Security, Black/Marines or Naval Trooper Officers, and I'd even dig other colors from EU too.
In the realm of obscurity I'd really like seeing the lower level officer guys seen walking the Death Star's halls too, who have their pants over their shoes, and at least some seem to have a different cut of the tunic.
There's some really weird variations on uniforms in those first 2 films though, between both sides even. ROTJ introduces some more but they seem to have no real rhyme or reason to them.