On my laptop, it looks to be an extremely pale metallic green.
I check any 53a Aston Martins which are not obviously metallic green (or metallic red for that matter!

), and usually rely on the baseplate photograph, the undersides of the bumpers and the rivet wells being the bast places to look for original colour. In the case of this particular model, I
think I can see pale green inside the rivets.
You should check the radiator grill on the model. If it has silver trim, the model was originally pale green. (According to Nick's variation listing, the silver model does not carry silver trim simply because it had no need of it.)