I'm running Ubuntu 14.04.
After installing Processing, the program works, but the backgroung did not change simultaneously.
When I move the potentiometer, background stays the same.
To change the Backgroung I have to stop the script in Processing, and run again.
Now it shows the new background.
For the Arduino code, if I modified the delay(1) code to be delay(100) in the loop() function, everything seemed to work very smoothly. My best guess is that the delay(1) is pushing serial data into the PROCESSING buffer faster than it can be retrieved, and this is resulting in the PROCESSING app not seeing the current data quickly enough to be responsive. I'm running under OS X (Yosemite) 10.10.2.
RussellD:
For the Arduino code, if I modified the delay(1) code to be delay(100) in the loop() function, everything seemed to work very smoothly
THIS !!!! This is the answer - I was facing the exact same issue with the Processing code not reacting in a timely fashion. Changing the delay to 100 sorted me out instantly - Thanks @RussellD