The rules here are really very simple!
It's a basic Sudoku with 1 to 9 appearing in every row, column and each of the nine blocks, although not diagonally (no large 'X'). All numbers that are higher than their abutting non-diagonal cell neighbours in the same block are in the pink cells. All numbers that are lower than their abutting (non-diagonal) cell neighbours in each block are in the blue cells. (The colour relationships do not apply between adjacent blocks!!)
That's it! Definitely enough to get any self-respecting hard-core Sudoku fanatic started with a combination of some logical thinking and standard Sudoku techniques.
Note: Graphic is a "jpg", xhtml generated by brianjn.