int red = 13;
int green = 12;
int button = 8;

void setup() {
  //Sets the red and green leds as outputs and the button as an input
  pinMode(red, OUTPUT);
  pinMode(green, OUTPUT);
  pinMode(button, INPUT_PULLUP);
  //Has the red light on at the start
}

void loop() {
  //Checks if the button has been pushed
  //Turns the red led off and the green led on
 if (digitalRead(button) == LOW) {
   digitalWrite(red, LOW);
   digitalWrite(green, HIGH);
 }
 //Turns the green led off and the red led on
 else{
   digitalWrite(red, HIGH);
   digitalWrite(green, LOW);
 }
}