Other people here can probably tell you better, but, a bird regurgitating because it loves you will throw up undigested seeds or pellet mush from its crop. A bird throwing up actual vomit is a sick bird. If the bird is bobbing its head to bring up food, its trying to feed you. If it throws up with little effort, that's a sick bird. Anything wierd colored or smelling, is from a sick bird. Remember colored pellets will produce that colored mush.