Pues encontré esto:
Description
Only recently recognised as a distinct species, variations in the scales on the head led to the Oman saw-scaled viper being split from the wider ranging Arabian saw-scaled viper (Echis coloratus) (3). The head is broad, with large eyes featuring vertical-slit pupils, and jaws that bear long, hinged, hollow fangs capable of administering a highly toxic venom (2). The overall colouration is grey or grey-brown, with paler blotches on the upper surface, running down the spine. Each blotch is surrounded by a dark border, which may extend laterally over the flanks, merging with a series of dark bands that run along each side. The underside is yellowish-white or greyish-white, and marked with indistinct dots in some individuals (3).
http://www.arkive.org/oman-saw-scaled-viper/echis-omanensis/description.html
O sea, que recientemente se catalogó la coloratus como tal, pudiendose conseguir ambas en Oman, pero ciertas características encontradas al estudiar taxonomía llevaron a considerarla una variación de la omanensis, incluso el artículo habla de diferente especie.
Para los efectos sirve tu respuesta, por que a ver quién es el wapo que ve la diferencia en una foto entre ambas!!