Percy

Percy is a Blue Guy that is mentioned in Hippo Story 4 and My Adventure in Sammy's Blue World. He seems to be the leader of all the Blue Guys, and has not appeared in any books. It is possible his name comes from Percy from Thomas and Friends, or even Percy Jackson.

Hippo Story 4
While talking about his world to George Aigaigy and Splatter Baby, King Sammy says "and then there's the Blue Guys. Lead by Percy, big angry noob from Sammy Game City."

My Adventure in Sammy's Blue World
He is mentioned indirectly by Chugs as "the leader".