void setup() {
  Serial.begin(9600);
  pinMode(4, OUTPUT);
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  randomSeed(analogRead(A0));
}

void loop() {
  int ran = random(1,7);
  if (ran == 2) {
    Serial.println("zelena");
    digitalWrite(ran, HIGH);
    delay(1000);
    digitalWrite(ran, LOW);
  }
  else if (ran == 3) {
    Serial.println("modra");
    digitalWrite(ran, HIGH);
    delay(1000);
    digitalWrite(ran, LOW);
  }
  else if (ran == 4) {
    Serial.println("cervena");
    digitalWrite(ran, HIGH);
    delay(1000);
    digitalWrite(ran, LOW);
  }
}