"Pied beauty" is a kind of beauty characterized by mixture, blending, and contrast. To be "pied" is to have two or more colors in dots or splotches. The famous "Pied Piper" was so named because his clothes were made from parts of many different-colored clothes. The word "piebald" comes from the same root, and it has a similar meaning: both are good SAT words! When you hear "piebald," think Snoopy, that lovable cartoon beagle with the black-and-white splotches.
Here's an interesting question: is the title saying that all beauty is mixed or "pied," or that "pied beauty" is just one kind of beauty?