What ya-all know about refrigerant dye?

I recently ran across a YouTube video where this guy is claiming that "most modern vehicles" already have dye in the AC system. Anybody know if this is true? I'm thinking of buying a black light (ultraviolet) now that you can get them cheap, LED..............

Also "what" do I need to know to buy a black light? Are the cheap China ones "usable?" Or do I need to research around?

Bear in mind this is for "very" occasional use.................