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,HIGH);
    digitalWrite(yesil,HIGH);
    digitalWrite(mavi,HIGH);
     delay(gecikme);
    break;
  }
}