const int Merah=2;
const int Kuning=3;
const int Hijau=4;

void setup() 
{
pinMode(Merah, OUTPUT);
pinMode(Kuning, OUTPUT);
pinMode(Hijau, OUTPUT);
}

void loop() 

{
digitalWrite(Merah, HIGH);
digitalWrite(Kuning, LOW);
digitalWrite(Hijau, LOW);
delay(500);
digitalWrite(Merah, LOW);
digitalWrite(Kuning, HIGH);
digitalWrite(Hijau, LOW);
delay(500);
digitalWrite(Merah, LOW);
digitalWrite(Kuning, LOW);
digitalWrite(Hijau, HIGH);
delay(500);
digitalWrite(Merah, LOW);
digitalWrite(Kuning, HIGH);
digitalWrite(Hijau, HIGH);
delay(500);
}