void setup() {
  pinMode(9, OUTPUT); 
  pinMode(10, OUTPUT);  
  pinMode(11, OUTPUT);
}
void loop() {
  accion(HIGH, LOW, LOW); 
  accion(LOW, HIGH, LOW);  
  accion(LOW, LOW, HIGH);
}
void accion(int rojo, int amarillo, int verde){
  digitalWrite(9, rojo); 
  digitalWrite(10, amarillo);  
  digitalWrite(11, verde);
  delay(4000);
}