int gruen = 13;
int rot = 12;
int blau = 11;

void setup() {
  pinMode(gruen, OUTPUT);
  pinMode(rot, OUTPUT);
  pinMode(blau, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int helligkeit = analogRead(A0);  // LDR ist an AO angeschlossen
  Serial.println(helligkeit);
  delay(100);
  if (helligkeit > 600) {
    digitalWrite(gruen, HIGH);
    digitalWrite(rot, LOW);
  }
  else if (helligkeit < 100) {
    digitalWrite(rot, LOW);
    digitalWrite(gruen, LOW);
    digitalWrite(blau, HIGH);
    delay(20);
    digitalWrite(blau, LOW);
    delay(20);
  }
  else  {
    digitalWrite(rot, HIGH);
    digitalWrite(gruen, LOW);
  }
}