int red=19, orange =5, green=15;
void setup() {
   Serial.begin(115200);
   pinMode(red, OUTPUT);
   pinMode(orange, OUTPUT);
   pinMode(green, OUTPUT);
}

void loop() {
  switchOnLED(red);
  switchOnLED(orange);
  switchOnLED(green);
}

void switchOnLED(int LED) {
  digitalWrite(LED, HIGH);
  delay(2000);
  digitalWrite(LED, LOW);
}