http://www.deviantart.com/deviation/29256742/ for clarification on its parent races.

Cuhaul and Coera, although at one time a single race, have difficulty successfully breeding with each other. About seventy percent of such unions are infertile, and twenty nine percent end in a stillbirth, often early in the term. However, once in a great while such a union bears fruit, and a Grue is the result. Grue stand between 5'6" and just over 6', and weight anywhere between 120-160 lbs. They lack the characteristic blue pigment in their fur, which is uniformly dark (in fact "grue" is an old Val'lendran word meaning "dark one") and their eyes are always a fiery shade of orange or yellow. Because they are so rare, Grue are not a true-breeding race and are regarded by their parent races as oddities. At best this can sway the Grue towards careers away from their own kind, and at worst they become vengeful outcasts. This latter tendency is both more prevalent and disturbing, as Grue share a strong connection to the Force, and hold no reservations about tapping into its Dark Side.