void setup() {
 Serial.begin(9600);
 Serial.println("Zadajte farbu led.");
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  digitalWrite(2, HIGH);
  digitalWrite(3, HIGH);
  digitalWrite(4, HIGH);

}

void loop() {


 if(Serial.available())
 {
  String farba = Serial.readStringUntil('\n');
  Serial.println(farba);
  clearBuffer();
  if(farba == "cervena")
  {
    digitalWrite(4, HIGH);
    digitalWrite(3, HIGH);
    digitalWrite(2, LOW);
  }
  else if(farba == "modra")
  {
    digitalWrite(4, LOW);
    digitalWrite(3, HIGH);
    digitalWrite(2, HIGH);
  }
  else if(farba == "zelena")
  {
    digitalWrite(3, LOW);
    digitalWrite(4, HIGH);
    digitalWrite(2, HIGH);
  }
 }

}

void clearBuffer()
{
  delay(2);
  Serial.read();
}