Those are all the colours that MGR show as being original paint jobs, which are either stated as being "green" or look green to me on photos I've seen. Not just Monograms, as such.
I agree about Black Olive, but the only car I have seen close up, I swore was black, whilst the owner stood right next to it was saying "are you blind? It's dark green ...". The Dutch car-papers he showed me do in fact say it is "Green", so MGR Nederland thought it was too, back in 2005.
I have a similar problem with Nocturn; maybe just that my eyesight is bad!
I find it difficult to put a single word colour to my Chatsworth R75V8 even. Some say 'Gold', some 'Green' the Dutch car-papers show it as simply 'Brown'. I don't like that, so 'Olive' is the best description I can come up with, hence her name.
David