The black comma is a black ring surrounding the eye, with a backwards pointing leg at the bottom. Each side of the comma is surrounded by a yellow ring that is discontinuous at both the top and the bottom. Hence the name “Yellow-faced”. The species also has a thin black line from nostril to nostril, also edged with yellow (below). Demansia psammophis.
Blue
I should also mention that there another 12 species of whip snake here, most of which have a “black comma” of some description. They either have obvious additional head marking or the leg on the comma sweeps further back and where bordered by yellow, the yellow is about double or more the length for D. psammophis.