You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For consistency, answers should be in all lower cased letters.

Category: THIS "BUD"'S FOR YOU 
Clue: It's the practice of pairing swimmers, with each responsible for the other's safety
the buddy system

Category: YELLOW THERE! 
Clue: A sushi favorite, hamachi is this type of fish
the yellowtail

Category: CELEBRITY PAINTERS 
Clue: Perhaps he made his old blue eyes a touch bluer in works found in his book "A Man and His Art"

frank sinatra