int kirmizi=9;
int yesil=10;
int mavi=11;
int renk;
int gecikme=1000;

void setup(){
  pinMode(kirmizi, OUTPUT);
  pinMode(yesil, OUTPUT);
  pinMode(mavi, OUTPUT);
  Serial.begin(9600);
}
void loop(){
  renk=random(4);
  Serial.println(renk);

  switch(renk){

    case 0:
    digitalWrite(kirmizi, HIGH);
    digitalWrite(yesil, LOW);
    digitalWrite(mavi, LOW);
    delay(gecikme);
    break;

    case 1:
    digitalWrite(kirmizi, LOW);
    digitalWrite(yesil, HIGH);
    digitalWrite(mavi, LOW);
    delay(gecikme);
    break;

    case 2:
    digitalWrite(kirmizi, LOW);
    digitalWrite(yesil, LOW);
    digitalWrite(mavi, HIGH);
    delay(gecikme);
    break;

    case 3:
    digitalWrite(kirmizi,LOW );
    digitalWrite(yesil, LOW);
    digitalWrite(mavi, LOW);
    delay(gecikme);
    break;
  }
}