Hey Anton... Who at Scum told you to basically piss off? Friggin' morons...

Anyway, here's some food for thought from the EU...
The "Imperial Army" is a specific branch of the Imperial military. Specifically, the Imperial Army uniform is listed as just, basically, an AT-ST Driver. Add some body armor ala Veers (sans the rank plaque), and you have the gist of what the Imperial Army wear...
That said, officers it's easy to assume would be no different than what we've seen established from the films. IE: Veers is a General in Battle Dress... So I'd say an Imperial Army Captain would be in the tunic and you'd be well within bounds to run with that. The COLOR of the tunic is the question... Veers wears the traditional grey-green, he's an army officer, so one could ASSUME you could simply modify a Jerjerrod who is in the same uniform essentially and slap body armor onto him. You could even choose to use the armor of a Death Star Gunner, but I prefer the "Veers" armor w/modified (or no) rank insignia as the "Imperial Army" standard being as the DSG's armor is more Stormtrooper-ish in nature.
Now, that's what I'd go with... Comic art establishment of EU Imperial military uniform colors is all over the place so I tend to view it with artistic liberties being taken...
Video games on the other hand seemingly establish the ranks of the Stormtroopers and the ranks of the Imperial Army being separate, and Stormtrooper Officers/Naval Troopers sharing the black uniforms/tunics (IE: Stormtroopers officers in dress uniforms wear black, ala a DST uniform or "Naval" uniform). They all answer to higher officers in the grey, but I think the army's military officers wear the grey tunics all the way down the line... If this is making any sense to you at all.
There's ways to fit in other colors and things... I think the VERY green uniforms though sometimes get overdone and are a product of EU comic artists not being consistant in their designs so I view them more as a flaw and inaccuracy than anything else...
So, in short...
I'd run with a simple Jerjerrod (readily available, best height/generic sculpt, as articulated as Veers basically), and if you have access to a POTF2 Veers you could hollow his body armor (front and back) out to fit over your Captain's body.
I'd avoid Veers because A) no back portion, B) his body is less "generic" due to the height issue (he is a tall character so he's good for that character, bad for "army building"), and C) his arms seem less "neutral" posed as well.
You can add a pack to your Captain if he's a field trooper too... A Sandtrooper pack is, to me, the Imperial basic field pack as it's modular design implies it is used for MOST environments, just modified witht he proper gear for the world.
That's my take on the figure... You'd need to modify a rank bar. I can't, offhand, recall what's what on their ranks badges but charts of them are out there to look at.
On the Imp Uniform colors though... There's tons. None of it's hashed out at all, EU confuses the issue further (brown/mustard uniforms, varying shades of green from super dark hunter greens to olive drab and more film-accurate colors), and it's tough to hash out... The only EU source that tried to lay down specifics to the Imp. Army was the old WEG RPG and they focused more on the troopers in the army and less on Officers, but I think Veers gives us a strong basis on Officers looks and some games have implied that the Imp. Army wears the grey-green of the films like Veers.
Lots to digest and lots of room for debate/creative license.