boolean listButton = false;
boolean currentButton = false;
boolean ledOn = false;

void setup() {
  // put your setup code here, to run once:
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
}
int b = 0;
int a = 0;

void ALL_OFF() {
  digitalWrite(4, false);
  digitalWrite(5, false);
  digitalWrite(6, false);
}
void ON(int a){
    digitalWrite(a, true);
}
void loop() {

  if (a == 0) {
    ALL_OFF();
    currentButton = debounce(listButton);
    if (listButton == false && currentButton == true) {
      ledOn = !ledOn;
      a++;
    }
    listButton = currentButton;
    ON(4);
  }

  if (a == 1) {
    ALL_OFF();
    currentButton = debounce(listButton);
    if (listButton == false && currentButton == true) {
      ledOn = !ledOn;
      a++;
    }
    listButton = currentButton;
    ON(5);
  }

  if (a == 2) {
    ALL_OFF();
    currentButton = debounce(listButton);
    if (listButton == false && currentButton == true) {
      ledOn = !ledOn;
      a++;
    }
    listButton = currentButton;
    ON(6);
  }

  if (a == 3) {
    a = 0;
  }
}

boolean debounce(boolean last) {
  boolean current = digitalRead(2);
  if (last != current) {
    delay(5);
    current = digitalRead(2);
  }
  return current;
}