void setup() {
  Serial.begin(9600);
  Serial.println("");
}

void ifvar(int ledpin, int onoff, int ddelay) {
  digitalWrite(ledpin, onoff);
  delay(ddelay);
}

void loop() {
  if (Serial.available() > 0) {
    String command = Serial.readString();
    command.trim();
    if (command == "red") {
      ifvar(2, 1, 400);
      ifvar(2, 0, 400);
      ifvar(2, 1, 400);
      ifvar(2, 0, 400);
    }

    if (command == "green") {
      ifvar(3, 1, 400);
      ifvar(3, 0, 400);
      ifvar(3, 1, 400);
      ifvar(3, 0, 400);
    }

    if (command == "blue") {
      ifvar(4, 1, 400);
      ifvar(4, 0, 400);
      ifvar(4, 1, 400);
      ifvar(4, 0, 400);
    }
  }
}