Tracking Color and Difference

We have a patch that uses jit.op to find the difference between the previous and current matrices, and a patch that tracks colors.

Our problem is that we will be recording a white wall with colored splotches, and when we throw a ball at the wall we want the matrix to only see the color of the ball and ignore the still colors already there. But the jit.op differencing does not really register color enough to be able to track it.

I don't really have a specific question, we are just stumped at how to do this. At first we thought of setting it to where when the ball hit the wall the projector would flash white so the camera would only see the ball, but with delays in the webcam and the program it would be very difficult to get it right. If the patch only picked up the movement on the camera then it could ignore the splotches already there. Is there any other method of tracking the difference between frames? Or is there a way to get more information out of the jit.op object?

Thanks