A very quick attempt to draw the Observer’s colour palette between classes!
Basically, the entire thing is mostly a deep greenish blue. The head horns, spikes, and ears have subtle light blue on the end and both the ears and the rest of the forehead section are a little lighter than the rest of the body. The patagium is close to the light blue colour but a little darker and greener, and the “boss” (upright) form has a V-shaped marking across its chest that is a sign of dominance and absent in the quadrupedal form.
The creature’s four “eyes”, which are not supposed to look super eye-like but are kind of shiny and gem-like, glow brightly, and they’d glow even more brightly when the creature is experiencing strong emotion of any kind. The “eyes” could probably turn different colours, but they don’t really have a standardised code of using any particular colours to communicate.