int red=8;
int yellow=9;
int green=10;

void setup() {
  pinMode(red, OUTPUT);
  pinMode(yellow, OUTPUT);
  pinMode(green, OUTPUT);

}

void loop() {
  digitalWrite(red,HIGH);
  digitalWrite(yellow,LOW);
  digitalWrite(green,LOW);
  delay(5000);

  digitalWrite(red,LOW);
  digitalWrite(yellow,HIGH);
  digitalWrite(green,LOW);
  delay(5000);

  digitalWrite(red,LOW);
  digitalWrite(yellow,LOW);
  digitalWrite(green,HIGH);
  delay(5000);
}