void setup() {
  pinMode(0, INPUT);   //THE BUTTON
  pinMode(1, OUTPUT);  //RED PIN
  pinMode(2, OUTPUT);  //GREEN PIN
  pinMode(3, OUTPUT);  //BLUE PIN
}
void loop() {

  if (digitalRead(0) == HIGH) {
    digitalWrite(3, HIGH);
    digitalWrite(2, LOW);
  } else {
    digitalWrite(2, HIGH);
    digitalWrite(3, LOW);
  }
}