You can assume that they looked like a ragpicker's delight. With that sort of attrition there would have been no capability to maintain a supply of uniforms (even if it had been intended to do so). The men would use whatever kit they could. It's a dead certainty that little of any clothing they wore from depot would still be serviceable. Therefore they would have a mish-mash of whatever was kept in repair, items taken from the dead (of all units and nationalities), local procurement and anything that was actually supplied by the system.
As the units shrank, officers might have made an attempt to maintain some uniformiyy of regimental and company distinctions, though this would be an uphill struggle. Imagine two different scenarios. 1) a soldier is amalgamted into some light company. Just where is he to get the requisite accoutrements? 2) an NCO is transferred from a battalion with an adequate quantity to one in short supply. How would you prevail on him to give up his current kit if nothing is available for new issue, especially when that NCO has probably worked to keep his kit in good order. These men were living in what they wore, plus what little spare clothing they had in their packs ... for years ... in all kinds of weather.
I think you'd be lucky to even know that a soldier was from Westphalia at first glance.