Colby is a character appearing in Professor Layton and the Unwound Future. He works as a constable at the Scotland Yard office. He is apparently a great fan of Professor Layton and his work. He works at the gate for Scotland Yard so he doesn't get to see much "action" like Barton does. Colby reappears in Professor Layton and the Last Specter when Emmy visits London to find help from Inspector Clamp Grosky. Colby offers assistance in directing Emmy to where Grosky has gone.
Puzzles
Colby, running the entrance to Scotland Yard, "makes" anyone who wants to go through solve his puzzle. This puzzle is "A Dangerous Place". It turns out that he actually was just testing Professor Layton's wits as Colby admires the professor's intellect.
Images
Profile in Unwound Future.
Profile in Last Specter.