Bones from Tlatelcomila (Tetelpan, México D.F.) were characterized by several complementary physical and chemical techniques, such as X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, energy‐dispersive spectroscopy and ultraviolet spectroscopy, to determine whether they were boiled or grilled. The usual correlation between thermal treatment and colour is revisited in terms of microscopic structure, morphology and texture. At temperatures less than 100°C, it is shown that colour depends not only on temperature or diagenesis but also on the cooking procedure; that is, on the presence of spice dyestuffs such as axiote (Bixa orellana) or chilli (Capsicum).