byte rojo = 3;
byte amarillo = 4;
byte verde = 5;

void setup() {
  pinMode(rojo, OUTPUT); 
  pinMode(amarillo, OUTPUT); 
  pinMode(verde, OUTPUT); 
}


void loop() {
  digitalWrite(rojo,1);
  delay(1000);
  digitalWrite(rojo,0);
  delay(1000);
  digitalWrite(amarillo,1);
  delay(1000);
  digitalWrite(amarillo,0);
  delay(1000);
  digitalWrite(verde,1);
  delay(1000);
  digitalWrite(verde,0);
  delay(1000);
}