Here are two more up close and personal views of the D4Y tailfin from Ken Glass. These detail images show very clearly the brush painted code numbers and stencilling details in both black and white.
The strong olive brown caste to the paint is illusory and caused by the film/processing. It demonstrates how colour photographs can be persuasive but ultimately misleading. The actual deep black green colour, with surface variegation and fading on this example, is sometimes described as "oil green" in contemporary documents. Nowadays "oil green" is often used to describe a lighter, slightly greyish green - like a sage green - but then it was more usually a term meaning a very dark green of strong chromatic intensity.
Image credit: © 2009 Ken Glass