For a project, I have found that I wish to learn about the color theory of warning signs and labels, specifically those that use colors across a spectrum that indicate an increasing intensity or different expected approach of some kind such as the DEFCON alert states and the "safety square".
However, I have found myself in the bit of the familiar issue of wanting to know more on a topic but not knowing the proper search terms to use to find out more on that topic. Not really knowing what else to do, I've come here.
So for that matter, I am asking: what kind of resources can I use to find out more about the color theory of warning signs, labels, alert states, etc.?