I mean yeah, that yellow bird, he's mad. He might be a bit too mad in fact, like maybe this whole egg situation is just a convenient excuse for him to vent some unresolved issues. So I guess that's legitimate anger, even if it's less about those pigs and more about his relationship with his father.
Red bird might be a little angry, but mostly he seems to be there out of a sense of obligation. I've got a feeling yellow bird talked him into it, calling him a coward and stuff like that until he grudgingly agreed to come along.
But blue bird? Blue bird isn't angry because blue bird has no idea what's going on. And he never has. He honestly just saw that big slingshot and, in his compromised state, thought it sounded like fun. Either that or yellow bird promised him some Cheeto's.
You could make the case that black bird is angry, he certainly seems to enjoy his role in all of this. But that's the thing, he enjoys it. I think black bird may simply be a psychopath. He's going to blow something up no matter what, this is just a good opportunity.
White bird seems like he's just scared out of his mind. White bird just wants to go home, and flies away with genuine relieve each time his attack is done.* Yellow bird threatened him, that's the only explanation.
Green bird is pretty clearly a weirdo. He's basically that kid from school who would occasionally show up wearing one of his mom's hats, or something. And he wouldn't explain or even reference it, cause he just loved that everyone found it strange. I'm not even sure what he's doing here, probably just knew it was good public place to show off how much of a weirdo he is. He's going to grow some kind of crazy mustache, trust me on this.
*Also, does anyone else find it weird that he drops eggs? I mean, isn't the whole point that they're trying to save eggs? How many eggs is it okay for him to plop on the ground in the service of saving the stolen ones?