Brief clarification: None of the Hunters use the same colors or birds in their names. Captain Eagle, Silver Hawk, Black Condor, and Red Falcon. Those are the main four, though I guess there might be other relatives in the family tree that inherited the Shout as well. Basically just pair up a color with a type of bird and that's how you're meant to know they belong to that Legacy. Only reason Rex didn't use a color was because he was a legit Captain in the US Army so he just used his rank... plus he was the first in the Legacy so he doesn't necessarily have to match up perfectly with his successors.