Color SudokuImage 

The aim of the canonical puzzle is to enter a color out of 1 through 9 in each cell of a 9?9 grid made up of 3?3 subgrids (called "regions"), starting with various colors given in some cells (the "givens"). Each row, column, and region must contain only one instance of each color. Completing the puzzle requires patience and logical ability.

 
Screenshot of Color Sudoku