There are several different shades of Olive Drab, and there is considerable variety of shade in the supply of those, plus many change colour over time.
Off the top of my head, you may be looking at US Olive Drab, British SCC15 olive drab (late war), BS381 Olive Drab (post war), Russian Forest Green, or NATO Green, or any of the other camo colours that are close to olive drab.
What is the project/period?