new color[] {
  color(100), color(150), color(200), color(250)
};


void setup() {
  size(400, 600);
  noStroke();
  cp5 = new ControlP5(this);
  for (int i=0;i<col.length;i++) {
    cp5.addBang("bang"+i)
       .setPosition(40+i*80, 200)
       .setSize(40, 40)
       .setId(i)
       ;
  }
  
  // change the trigger event, by default it is PRESSED.
  cp5.addBang("bang")
     .setPosition(40, 300)
     .setSize(280, 40)
     .setTriggerEvent(Bang.RELEASE)
     .setLabel("changeBackground")
     ;
         