Parkerized finish can be found too, in both grey and green, but examples of these are hard to find and I've never seen Panther ammo finished this way;
One would think that if they made KwK 43 and KwK 36 ammo Parkerized, Kwk 42 would be too, I've just never seen one. The brass ones could be either dull or polished and the brass-plated could be either brass or copper colored. Bare steel had a bad habit of sticking in the breach and not ejecting, making it unsuitable for use. Some of the lacquered shells look greenish, like the example on the far left;
Some look like ordinary steel, with a slight iridescence.
More examples of different colored lacquered steel and Parkerized casings;
http://www.network54.com/Forum/637977/thread/1275567962/last-1275648965/view+all+messages
KwK 42 rounds, note the more copper-colored plating on the top round, as opposed to the more typical yellowish brass;
This artwork from a French website depicts just exactly what I can't find in real life, green Parkerized KwK 42 ammo;
What basis in reality this has, I don't know, but it theoretically could have existed.