Brighter colors indicate health like their ability to successfully gather food which builds up the pigmentation, as well as fitness in avoiding predators. If you see bright bird it is very likely its a male, the stronger the signals, the more attractive they are as a potential mate

As a big fan of fallout, imo, 4 is the weakest of series. Engine was outdated, repeated time wasting quests, boring world building, the base building was their new exciting feature but it fell kinda flat. Now with 1k+ mods game can actually be a lot fun though. Also 74 didn’t exist.