If you read my guide, you probably saw that I repaired a broken case (you may be able to see it at the front bottom left) with JB Weld (the best epoxy there is) which is dark gray.
After that, I just went ahead and camouflaged the whole thing with "Dupli-Color" Charcoal Gray, which is called "coating" rather than paint, but it went on and behaved like paint. It is a pure and fairly "cool" gray.
The actual IBM industrial color is a strange voodoo mix of warm gray, medium brown, olive green, and who knows what else to achieve a magnificent and utterly neutral non-color. To my eyes, Unicomp's version is slightly brighter and greener than the old IBM hue.