Hi there
When Olive Drab was standarized in April 1944, in structions were quite clear that NO disruptive patterning was to be used.
The illusive Camouflage Chart No.15 apparently laid out all the approved patterns but I've heard of no-one ever laying eyes on one.
Military Training Pamplet No.46 Part IVa, is the usual fallback.
For further details, see:
http://milifax2003.tripod.com/home03.htm
Steve