Honestly I doubt there is any difference between current production T1.2's regardless of color. I think they tweaked the T1.2 at some point, but not sure when. It's not unusual for early and later run versions of a headphone to sound a bit different. It could be as simple as a slight material change in the pads, such as a different foam inside the earpads. It could also be slightly different dampening, etc. Heck even the very early DT 1990's have different pads than ones in later batches, this is like within months of release, this can be seen by the amount of holes on the back of the analytical pads and what seems to be a different foam in the balanced pads.
Very early DT 1990 pads.
Later DT 1990 pads.