int greenled = 3, redled = 4, buzzerPin = 5;

void setup()
{
  pinMode(greenled, OUTPUT);
  pinMode(redled, OUTPUT);
  pinMode(buzzerPin, OUTPUT);
  Serial.begin(9600);
  Serial.println("1. Green Light ON");
  Serial.println("2. Red Light ON");
  Serial.println("3. All Light OFF");
  digitalWrite(greenled, LOW);
  digitalWrite(redled, LOW);
  digitalWrite(buzzerPin, LOW);
}

void loop()
{
  Serial.println("Set your LED state:");
  while(Serial.available()==0){}
    int choice = Serial.parseInt();
    switch(choice)
    {
      case 1:
      if(choice == 1)
      {
        digitalWrite(greenled, HIGH);
        digitalWrite(redled, LOW);
        Serial.println("Green Light ON");
      }
      break;
      case 2:
      if(choice == 2)
      {
        digitalWrite(redled, HIGH);
        digitalWrite(greenled, LOW);
        digitalWrite(buzzerPin, HIGH);
        Serial.println("Red Light ON");
      }
      break;
      case 3:
      if(choice == 3)
      {
        digitalWrite(redled, LOW);
        digitalWrite(greenled, LOW);
        digitalWrite(buzzerPin, LOW);
        Serial.println("All Light OFF");
      }
      break;
      default:
      Serial.println("Want to operate LED again!");
    }
}