It was not the postcard-worthy aesthetics that prompted Greek islanders to first drench their cliffside-carved homes, churches, and pathways in a thick layer of pearly white paint. Much like wearing a white tunic on a hot sunny day, painting your house a shade of reflective white is a fine way to keep an ancient island cool, bouncing some of the sun’s heat back into space instead of absorbing it into the structure of the buildings themselves. Be…