Green.
This depends on what kind of birdfeeder you have and what you put in it. Seed-eating birds will come to a birdfeeder with...well, seed, obviously. These will vary depending on the kind of seed, and will include sparrows, finches, goldfinches, doves, nuthatches, and chickadees. Suet feeders will attract a variety - most of the birds mentioned will eat from them, and so will woodpeckers, sapsuckers, and bushtits. Peanut and other nut feeders will attract crows, ravens, and jays. Fruit will attract finches, robins and other thrushes, bluebirds, and waxwings. Sugar water will attract hummingbirds and orioles, and the occasional woodpecker or finch. And then there are the more omnivorous birds (such as the invasive European Starling) which will chow down pretty much anything you put out.
The most attractive color for a bird feeder is red. This color is known to attract birds, especially hummingbirds, due to its similarity to certain types of flowers that birds feed on. Yellow and blue can also attract birds, but red tends to be the most effective color choice.
Although hard to tell, anything made of wood will atract dust Perhaps your vacuum cleaner will have the most dust.
Blue Jays are attracted to the color blue. All birds are attracted to most bright colors, but certain birds are attracted to certain colors.
Green
Penguins eggs are a yellow colour.
Birds have a cloaca which is a holding area for both urinary (pee) and digestive (poop) waste, which are discharged together. Both can be altered in color by the things the birds eat, but most often the pee is white and the poop is green to brown.
The importance of shapes is that shapes are a buiding block to math or art .Most people use shapes to beatify and atract .
Birds that you see around in the daytime have phenomenal color vision. Birds see color not only better than humans, but they see color in such a superior way that we humans cannot even begin to understand it. Pretty much all daytime birds can see blue perfectly. Nighttime birds, like owls, are most likely colorblind, though.
Some you can tell by color or plumage. A vet can do a physical exam and look at the plumbing. A DNA test is the most certain.
The smallest bird if the bee hummingbird and the female one is like a greenish color up in the neck area with the rest being white while a male is a fiery red in the neck and a whitish gray below.
The dodo birds were not brown, they were most usually a light brown color with black beaks. Some of there beak is an orangey-brown as well.