Monarch butterflies eat milkweed, which makes predators noxious, and then avoid them. Viceroy butterflies, on the other hand, are delicious to eat (allegedly). The Viceroy has evolved the orange and brown coloring similar to Monarchs, which helps them survive, since Viceroys get mistaken for Monarchs, and thus aren't eaten. This is a classic example of what type of mimicry?
Batesian (mimicry)