Karadoku

If you like Sudoku, then you'll love Karadoku. Karadoku is just like Sudoku, only using colors in stead of numbers.
So the rules are that only one of each color in each 3x3 square and the same in each row and each column until the board is complete with no white squares left. Multiple colors are possible to make note of possible solutions, but will not be considered as a complete board.