now really i don\'t think this is a big problem, i am painting a kroot shaper ( my first commision) and i don\'t know what colour to paint the eyes, if they should be like human eyes or red or something like that??
Just had a look at the codex and the collector\'s guid and they\'re not human-like. They\'ve been painted in one colour (no iris). Most seem to be pale blue but there are red ones too.
Avian or Alien is the go with them ..or how about avian alien??
basically pick a colour that will stand out and put a bit of character in the face....Yellow ,,light blue...any ya want really..Have you asked the person your painting for what colour they would like??