“Why Do Blue-Eyed Men Prefer Women with the Same Eye Color?” Bruno Laeng, Ronny Mathisen and Jan-Are Johnsen, Behavioral Ecology and Sociobiology, vol. 61, 2007, pp. 371–84( http://dx.doi.org/10.1007/s00265-006-0266-1). The authors, at the University of Tromso, Norway, report:
“Close-up photos of young women and adult men with either blue or brown eyes were rated for their attractiveness by young women and men observers with either blue or brown eyes (N=88). The eye color in the photographs of each model was manipulated so that a same face would be shown with either the natural eye color (e.g., blue) or with the other color (e.g., brown)….
“[Our results] suggest the presence of a male adaptation for the detection of extra-pair paternity based on eye color, as a phenotypically based assurance of paternity (i.e., when the father’s and offspring’s phenotypes match) as well as a defense against cuckoldry (i.e., when the phenotypes do not match).”
(That’s an excerpt from the article “Colorful Research,” published in AIR 14:4.)