Kirby was supposed to be the fifth member of the Ninja Turtles gang in the fourth TMNT movie, (TMNT: The Next Mutation) which was cancelled. He was going to be a turtle from another dimension. He was named after an American comic book artist, Jack Kirby. In various concept art, his bandana color is shown as white, black, and purple. Of note, Kirby has one more fingers and toes than the other Turtles in most concept art. According to Teenage Mutant Ninja Turtles: The Ultimate Visual History, he could have potentially be used as a fifth member of the team in Ninja Turtles: The Next Mutation, but Saban Entertainment refused to do the series unless there was a female Turtle.
See Kirby (Turtle)/Gallery and Kirby (Turtle)/Fan Art