In 1984, archaeologists discovered an important group of mural paintings at the site of Cacaxtla, Mexico. Research has been undertaken to analyze the Prehispanic pigments and the painting techniques employed in these paintings. The present work is focused on the use of colors in these paintings by means of optical microscopy (OM) and transmission electron microscopy (TEM). The stratigraphic structure of painting layers support the presence of an organic binding media. In addition, Maya blue is for the first time described physically by TEM.