(click for larger image)
The fact that Medea is in stark black & white while the rest of the piece is in pastel colors is supposed to represent several things:
1) Medea's extreme personality, which doesn't seem to have any 'middle gears.' She's madly in love with Jason, and kills to help him. Then when he betrays her she hates him passionately, and she kills to hurt him. Nothing in the middle, just an abrupt plunge from the deepest love to the deepest hate.
2) Medea's foreignness, and the fact that ultimately she essentially doesn't fit in with Greek ideas of womanhood, allowing her to do what she did.
(Personally, I don't think the colored pencil bits turned out very well at all, but oh well...)