You are a student at Shiz University because you have the potential to wield magic powers. During the first days of being on campus, you are among a crowd of students going about their business when you hear a gasp come out of Glinda (or that popular girl in the pink dress). You wonder what is going on as you turn in the direction everyone else is and you spot a green skinned woman who self-consciously holds her books close to herself.

You're green. Glinda whispers in surprise I am. Elphaba answers