The Panzer IVD is an interesting choice since it first saw active service in May 1940 in France. Beginning production in October 1939 it saw combat in France, the Balkans, Greece, Africa, and Russia with the last of them phased out in early 1944.
So, the color you paint it depends on when, where, and what it's doing. Is it invading France in 1940 or training drivers at Paderborn in 1944? Pick a time frame, a unit or a task, and a theater. After that, anything's possible.
Panzer Voran!