In a recent study by Richard Russell of Harvard University, the two faces above were perceived as male and female. However, both faces are actually versions of the same androgynous face. One face was created by increasing the contrast of the face, while the other face was created by decreasing the contrast. The face with more contrast is perceived as female, while the face with less contrast is perceived as male.
I'm not sure that this proves much more than that pale skin and darker lips are usually interpreted as more feminine, but perhaps it also provides a useful printing (or make-up) tip, and a reminder that our visual perception is extraordinarily subtle.