void setup() {
  pinMode(4, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
}

void loop() {
  //red
digitalWrite(4, HIGH);  
delay(2000);
digitalWrite(4, LOW);
delay(500);

 //yellow
digitalWrite(10, HIGH);  
delay(2000);
digitalWrite(10, LOW);
delay(500);

 //green
digitalWrite(11, HIGH);  
delay(2000);
digitalWrite(11, LOW);
delay(500);

 //yellow
digitalWrite(10, HIGH);  
delay(2000);
digitalWrite(10, LOW);
delay(500);
}