Here is a figure from a neat article (PDF here) by Richard Russell illustrating how facial contrast and cosmetics can alter the perceived sex of an androgynous face.
The Illusion of Sex. The face on the left appears male, while the face on the right appears female. Both images were produced by making slight alterations to the same original image. The eyes and lips were unaltered, and hence equally dark in both images. The remainder of the image was darkened to produce the left image, and lightened to produce the right image. The eyes and lips may appear darker in the right image than in the left image, but are notöit is an example of simultaneous contrast.