The Eastern Tiger Swallowtail, along with the Monarch, is one of our most recognizable butterflies. You can identify it (usually) by its large size and bright yellow color with black tiger stripes.
Male tiger swallowtails have a few orange and blue spots near the tail.
Females have both a light and dark form. The light form (left) looks a lot like the male, except it has more blue on the hind wings. The dark form still has the blue spots, but it is otherwise very dark with no yellow.