#define RED 28
#define YELLOW 5
#define GREEN 9

void setup() {
  pinMode(RED, OUTPUT);
  pinMode(YELLOW, OUTPUT);
  pinMode(GREEN, OUTPUT);
}

void loop() {
  digitalWrite(GREEN, HIGH);
  digitalWrite(RED,LOW);
  delay(2000);

  digitalWrite(YELLOW, HIGH);
  digitalWrite(GREEN,LOW);
  delay(2000);

  digitalWrite(RED, HIGH);
  digitalWrite(YELLOW, LOW);
  delay(2000);

  digitalWrite(GREEN, HIGH);
  digitalWrite(YELLOW, LOW);
  digitalWrite(RED, LOW);
}