I've done a bit of research and under all the layers of paint on our UC there is SCC 15 Olive drab (also called US olive drab).
Cameron, please note SCC 15 Olive Drab is similar, but not the same as US Olive Drab. Search for Mike Starmer on this forum, buy one of his publications with a SCC 15 Olive Drab sample, take it to your paint supplier and have your paint mixed up.