Leonhard Euler from Switzerland came up with this puzzle. You have to choose the inside and outside color of each square, so every color (inside and outside count separatly) only exists once horizontal and vertical.
Easy 
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Tags: Puzzle, So Doku, New, New Puzzle
Happy Steve wrote,
AND it looks like you have to make each outside/inside color combination unique. For example, you cannot have two squares that have a red outside and a blue inside.
Link | July 17th, 2006 at 6:57 pm