That is one outstanding looking grey! I love the hat picture.
They are considered red factors or king congos. Folklore had it that they were treated like royalty when in the wild by the natives because they are thought to posess special powers. If you read the species profile I wrote about Congo african greys, it mentions it there.
Sydney is also a red factor and Mike is right that they are more common then people know. Alex, Dr Irene Pepperbergs grey, has a red signature feather on his shoulder/neck.
Wendy, our own Alleaa, had a grey that is a heavy red factor.
Beautiful birds for sure!