For me the penal legion troopers should wear parts of standard IG uniform. No one in their right mind would want to spend money on a bespoke uniform for the scum sentenced to the Penal Legions. If the squads continued to wear the uniform they were wearing when they were arrested, this could create a multicoloured rainbow legion, which to the military mind might not suggest punishment or proper discipline.
The IG would be unlikely to design and supply a bespoke uniform for these short lived troopers, yet the military would want uniformity of appearance if possible. The troopers would be unlikely too survive long enough for for than 1 or 2 to in any squad to be in rags.
In some legions as part of military discipline the Legion Quartermaster could have siezed the uniforms from all prisoners as they arrived have them dyed a dark grey to hide the grime and dirt and then redistribute them in the wrong sizes to the newly arrive troopers. This is what I have attempted to achieve with this squad.
The Custodian has a different uniform to distingish him from the criminals. It would be unlikely but not impossible in some circumstances for the custodian to be a criminal of the same magnitude as the troopers as he will have access to the explosive collar controls.
There is still a bit to go before the paint job is finished.