Digital reconstruction of ancient polychromy is a relatively recent phenomenon in the history of archaeological and architectural heritage documentation. It has emerged as a result of new interest in the experimental archaeology and the technological development of computer graphic tools. Therefore, this article presents a project aimed at the scientific reconstruction of the original polychromy and the realistic rendering of an ancient sarcophagus, obtained with the use of some open source tools. In particular, starting from the accurate study of a polychrome Roman sarcophagus (National Roman Museum in Rome, inv. no. 125891), we show how the MeshLab tool was used to support the polychrome reconstruction stage and how Blender (or, rather, a combination of MeshLab and Blender) was used to achieve a more sophisticated visual presentation of the current and reconstruction ancient colour. A central role has been given to the rendering of different and overlapped layers of paint.