int RED_LED = 2;
int YALLOW_LED = 8;
int GREEN_LED = 13;

void setup() {

pinMode(RED_LED, OUTPUT);
pinMode(YALLOW_LED, OUTPUT);
pinMode(GREEN_LED, OUTPUT);
}
void loop() {
digitalWrite(RED_LED, HIGH);
digitalWrite(YALLOW_LED, LOW);
digitalWrite(GREEN_LED, LOW);

delay(4000);
digitalWrite(RED_LED, LOW);
digitalWrite(YALLOW_LED, HIGH);
digitalWrite(GREEN_LED, LOW);
delay(2000);
digitalWrite(RED_LED, LOW); 
digitalWrite(YALLOW_LED, LOW); 
digitalWrite(GREEN_LED, HIGH); 
delay(4000);
digitalWrite(RED_LED, LOW);
digitalWrite(YALLOW_LED, HIGH);
digitalWrite(GREEN_LED, LOW); 
delay(2000);
}