I had a look around and found FS 36375 here: https://ams-std-595-color.com/. I'm sorry, but I couldn't really find when 36375 came into effect. However, it's Light Ghost Gray, which has been on F-14s, F-15s, F-16s, F-18s, and other aircraft. So, it's been around since at least the mid-80s, I believe.
Sorry I couldn't help you more.
Tom