#define GREEN 2 // Set to your green led pin
#define YELLOW 3 // Set to your yellow led pin
#define RED 4 // Set to your red led pin

void setup() {
  // No need to change any of this
  pinMode(GREEN, OUTPUT);
  pinMode(YELLOW, OUTPUT);
  pinMode(RED, OUTPUT);
}

void enableColor(String color) {
  // No need to change any of this either
  if (color.equals("red")) {
    digitalWrite(RED, HIGH);
    digitalWrite(YELLOW, LOW);
    digitalWrite(GREEN, LOW);
  } else if (color.equals("yellow")) {
    digitalWrite(YELLOW, HIGH);
    digitalWrite(RED, LOW);
    digitalWrite(GREEN, LOW);
  } else if (color.equals("green")) {
    digitalWrite(GREEN, HIGH);
    digitalWrite(RED, LOW);
    digitalWrite(YELLOW, LOW);
  }
}

void loop() {
  // You can change the delay
  enableColor("red");
  delay(2000); // This is not 2000 seconds rather 2000 ms (2 seconds)
  enableColor("green");
  delay(2000);
  enableColor("yellow");
  delay(1000);
}