#define GREEN_LED  A2
#define YELLOW_LED A1
#define RED_LED    A0

void setup() {
  pinMode(GREEN_LED, OUTPUT);
  pinMode(YELLOW_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);
}

void loop() {
  // GREEN - 3 sec
  digitalWrite(GREEN_LED, HIGH);
  digitalWrite(YELLOW_LED, LOW);
  digitalWrite(RED_LED, LOW);
  delay(3000);

  // YELLOW - 2 sec
  digitalWrite(GREEN_LED, LOW);
  digitalWrite(YELLOW_LED, HIGH);
  digitalWrite(RED_LED, LOW);
  delay(2000);

  // RED - 4 sec
  digitalWrite(GREEN_LED, LOW);
  digitalWrite(YELLOW_LED, LOW);
  digitalWrite(RED_LED, HIGH);
  delay(4000);
}