Why do some wings have such brilliant colors? Why are some so dull?
The colors of butterfly and moth wings may serve several purposes. Colors are often used in courtship, so that male and female butterflies recognize each other as the correct species. Bright colors may also serve to warn birds or other predators that a particular butterfly, such as a Monarch or a Pipevine Swallowtail, is bad-tasting. Other butterflies and moths, although perfectly edible, may have colors that "mimic" the bad-tasting species and thereby gain protection for themselves. Finally, certain color patterns may help the butterfly or moth blend into its background and be protected from birds or other would-be predators by background resemblance. These protective colors can be bright (like the Imperial Moth, below) and other species are dull in color (like the Goatweed Leafwing, below).
For information on how the wing colors are developed, see the question about dust.
The Imperial Moth (Eacles imperialis, above) shows that bright colors
can help an insect to blend in with the right environment.
The wings of the Goatweed Leafwing look like dead leaves,
so it is able to blend in on the forest floor.
Goatweed Leafwing photographs by Ken Childs.