In GNG anime he is a non-brindle silver Akita Inu and wears a dark brown collar.
In the first coloured pages of GNG manga in Shounen Jump he is light red with a black collar.
In a newer picture, he is seen as pure white and with a green collar.
Like Riki and Gin, Shiro is strong, brave, charismatic and well respected among humans and dogs alike.
Ginga Densetsu Riki
Shiro was Riki's father and Yamabuki's mate. He was owned by the hunter, Takeda Gohei, who had trained him into one of the best hunting dogs. Shiro saved Riki after he found him badly beaten up, drifting in the river, and told him how to become great.
On a hunt for the wild bear Akakabuto, Shiro and Takeda Gohee were ambushed and needed to struggle for their lives. As Riki rushed in to help, Shiro saw an option to save his owner and his son by pushing Akakabuto and himself into a ravine.
Ginga: Nagareboshi Gin
In the start of episode one, there is a flashback of Shiro and Takeda Gohee hunting Akakabuto. Gohee lost his ear in the battle against Akakabuto. Shiro attackd Akakabuto to protect him and they both fell into the valley, Shiro biting Akakabuto's muzzle. Akakabuto survived, but Shiro did not.