I like it. It's an interesting spin (haha) on sudoku.
the only issue I have is the game won't let you get it wrong. If I try to put the wrong color (or if I'm simply being lazy and trying to guess incorrectly), the game will not register that color, so I now know that the color placement is incorrect. In this case, you can lazily figure out the correct result by exhaustively placing colors in all the empty spots until it shows up (which means it is in the correct spot)
You probably should allow for incorrect placement to still change color, so you cannot gain information simply by being wrong.
Other than that... I like it a bunch.