The HE model is all OD with yellow markings on across the middle section of the warhead. The exception being the fins and the contact ring which are left pretty much bare steel. Should be three lines. One is (at the very top) type, caliber and model. The second one is the lot number, and the third one is temperature limits. This is called the M28A2 in my 1964 manual.
The "practice" round is painted that all blue practice paint with white lettering. On the warhead it has the same nomenclature in the same lines only in white.
This color code all changed sometime after 1964. It then went something like this: The HEAT went stayed od up to the point of reaching the warhead, then it was colored black with yellow markings on it. The "Practice" rounds remained the same throughout.
What else do you want to know?